diff --git a/glibc.spec b/glibc.spec
index b784655..ffb4260 100644
--- a/glibc.spec
+++ b/glibc.spec
@@ -78,7 +78,7 @@
 %endif
 
 # We do our own build flags management.  In particular, see
-# rpm_inherit_flags below.
+# glibc_shell_* below.
 %undefine _auto_set_build_flags
 
 ##############################################################################
@@ -1192,78 +1192,97 @@ cat /proc/sysinfo 2>/dev/null || true
 cat /proc/meminfo
 df
 
-# We build using the native system compilers.
-GCC=gcc
-GXX=g++
-
-# Part of rpm_inherit_flags.  Is overridden below.
-rpm_append_flag ()
-{
-    BuildFlags="$BuildFlags $*"
-}
-
-# Propagates the listed flags to rpm_append_flag if supplied by
-# redhat-rpm-config.
-BuildFlags="-O2 -g"
-rpm_inherit_flags ()
-{
-	local reference=" $* "
-	local flag
-	for flag in $RPM_OPT_FLAGS $RPM_LD_FLAGS ; do
-		if echo "$reference" | grep -q -F " $flag " ; then
-			rpm_append_flag "$flag"
-		fi
-	done
-}
-
 # Propgate select compiler flags from redhat-rpm-config.  These flags
 # are target-dependent, so we use only those which are specified in
 # redhat-rpm-config.  We keep the -m32/-m32/-m64 flags to support
 # multilib builds.
-#
-# Note: For building alternative run-times, care is required to avoid
-# overriding the architecture flags which go into CC/CXX.  The flags
-# below are passed in CFLAGS.
 
-rpm_inherit_flags \
-	"-Wp,-D_GLIBCXX_ASSERTIONS" \
-	"-fasynchronous-unwind-tables" \
-	"-fstack-clash-protection" \
-	"-fno-omit-frame-pointer" \
-	"-funwind-tables" \
-	"-m31" \
-	"-m32" \
-	"-m64" \
-	"-march=armv8-a+lse" \
-	"-march=armv8.1-a" \
-	"-march=haswell" \
-	"-march=i686" \
-	"-march=x86-64" \
-	"-march=x86-64-v2" \
-	"-march=x86-64-v3" \
-	"-march=x86-64-v4" \
-	"-march=z13" \
-	"-march=z14" \
-	"-march=z15" \
-	"-march=zEC12" \
-	"-mbackchain" \
-	"-mbranch-protection=standard" \
-	"-mcpu=power10" \
-	"-mcpu=power8" \
-	"-mcpu=power9" \
-	"-mfpmath=sse" \
-	"-mno-omit-leaf-frame-pointer" \
-	"-msse2" \
-	"-mstackrealign" \
-	"-mtune=generic" \
-	"-mtune=power10" \
-	"-mtune=power8" \
-	"-mtune=power9" \
-	"-mtune=z13" \
-	"-mtune=z14" \
-	"-mtune=z15" \
-	"-mtune=zEC12" \
-	"-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1" \
+%{lua:
+-- Split the string argument into keys of an associate array.
+-- The values are set to true.
+local function string_to_array(s)
+    local result = {}
+    for e in string.gmatch(s, "%S+") do
+        result[e] = true
+    end
+    return result
+end
+
+local inherit_flags = {}
+
+-- These flags are put into the CC and CXX arguments to configure.
+-- Alternate builds do not use the flags listed here, only the main build does.
+inherit_flags.cc_main = string_to_array [[
+-march=armv8-a+lse
+-march=armv8.1-a
+-march=haswell
+-march=i686
+-march=x86-64
+-march=x86-64-v2
+-march=x86-64-v3
+-march=x86-64-v4
+-march=z13
+-march=z14
+-march=z15
+-march=zEC12
+-mcpu=power10
+-mcpu=power8
+-mcpu=power9
+-mtune=generic
+-mtune=power10
+-mtune=power8
+-mtune=power9
+-mtune=z13
+-mtune=z14
+-mtune=z15
+-mtune=zEC12
+]]
+
+-- Like inherit_flags_cc_main, but also used for alternate builds.
+inherit_flags.cc = string_to_array [[
+-m31
+-m32
+-m64
+]]
+
+-- These flags are passed through CFLAGS and CXXFLAGS.
+inherit_flags.cflags = string_to_array [[
+-O2
+-O3
+-Wall
+-Wp,-D_GLIBCXX_ASSERTIONS
+-fasynchronous-unwind-tables
+-fno-omit-frame-pointer
+-fstack-clash-protection
+-funwind-tables
+-g
+-mbackchain
+-mbranch-protection=standard
+-mfpmath=sse
+-mno-omit-leaf-frame-pointer
+-msse2
+-mstackrealign
+-specs=/usr/lib/rpm/redhat/redhat-annobin-cc1
+]]
+
+-- Iterate over the build_cflags RPM variable and emit a shell
+-- variable that contains the inherited flags of the indicated variant.
+local function shell_build_flags(variant)
+    local result = {}
+    local inherit = assert(inherit_flags[variant])
+    for f in string.gmatch(rpm.expand("%build_cflags"), "%S+") do
+        if inherit[f] then
+	    result[#result + 1] = f
+	end
+    end
+    print("glibc_flags_" .. variant .. "=\"" .. table.concat(result, " ")
+          .. "\"\n")
+end
+
+shell_build_flags('cc_main') -- Set $glibc_flags_cc_main.
+shell_build_flags('cc') -- Set $glibc_flags_cc.
+shell_build_flags('cflags') -- Set $glibc_flags_cflags.
+}
 
 %if 0%{?_annotated_build} > 0
 # libc_nonshared.a cannot be built with the default hardening flags
@@ -1285,34 +1304,29 @@ BuildFlagsNonshared="-fplugin=annobin -fplugin-arg-annobin-disable -Wa,--generat
 # %%build - Generic options.
 ##############################################################################
 EnableKernel="--enable-kernel=%{enablekernel}"
-# Save the used compiler and options into the file "Gcc" for use later
-# by %%install.
-echo "$GCC" > Gcc
 
 ##############################################################################
 # build()
-#	Build glibc in `build-%{target}$1', passing the rest of the arguments
-#	as CFLAGS to the build (not the same as configure CFLAGS). Several
+#	Build glibc in the directory $1, passing the rest of the arguments
+#	as additional configure arguments.  Several
 #	global values are used to determine build flags, kernel version,
 #	system tap support, etc.
 ##############################################################################
 build()
 {
-	local builddir=build-%{target}${1:+-$1}
-	${1+shift}
+	local builddir=$1
+	shift
 	rm -rf $builddir
 	mkdir $builddir
 	pushd $builddir
-	../configure CC="$GCC" CXX="$GXX" CFLAGS="$BuildFlags $*" \
+	../configure "$@" \
 		--prefix=%{_prefix} \
 		--with-headers=%{_prefix}/include $EnableKernel \
 		--with-nonshared-cflags="$BuildFlagsNonshared" \
 		--enable-bind-now \
 		--build=%{target} \
-		${configure_host} \
 		--enable-stack-protector=strong \
 		--enable-systemtap \
-		${core_with_options} \
 %ifarch %{ix86}
 		--disable-multi-arch \
 %endif
@@ -1347,17 +1361,23 @@ build()
 
 %ifarch x86_64
 # Build for the glibc32 package.
-GCC="$GCC -m32" GXX="$GXX -m32" BuildFlags="${BuildFlags/-m64/-m32}" configure_host="--host=i686-linux-gnu" build 32
-%endif
-
-configure_host=""
-
-%ifarch x86_64
-configure_host="--enable-cet"
+build build-%{target}-32 \
+  CC="gcc -m32" \
+  CXX="g++ -m32" \
+  CFLAGS="${glibc_flags_cflags/-m64/-m32}" \
+  --host=i686-linux-gnu \
+#
 %endif
 
 # Default set of compiler options.
-build
+build build-%{target} \
+  CC="gcc $glibc_flags_cc $glibc_flags_cc_main" \
+  CXX="gcc $glibc_flags_cc $glibc_flags_cc_main" \
+  CFLAGS="$glibc_flags_cflags" \
+%ifarch x86_64
+  --enable-cet \
+%endif
+#
 
 ##############################################################################
 # Install glibc...
@@ -1373,9 +1393,6 @@ build
 # Remove existing file lists.
 find . -type f -name '*.filelist' -exec rm -rf {} \;
 
-# Reload compiler and build options that were used during %%build.
-GCC=`cat Gcc`
-
 %ifarch riscv64
 # RISC-V ABI wants to install everything in /lib64/lp64d or /usr/lib64/lp64d.
 # Make these be symlinks to /lib64 or /usr/lib64 respectively.  See: