Build using clang

firefox.spec

@@ -1,6 +1,7 @@
 # Set for local builds only
 %global disable_toolsets  0
 
+%global build_with_clang  1
 %ifarch i686
 # no debug package for the i686 because oom on i686 with debuginfos
 %global debug_package %{nil}
@@ -380,6 +381,9 @@ BuildRequires:  llvm-toolset-%{llvm_version}-llvm-devel
 %if ! 0%{?use_bundled_yasm}
 BuildRequires:  yasm
 %endif
+%if %{build_with_clang}
+BuildRequires:  lld
+%endif
 
 
 %if 0%{?use_bundled_python_2}
@@ -1099,6 +1103,7 @@ export MOZ_DEBUG_FLAGS=" "
 # We don't wantfirefox to use CK_GCM_PARAMS_V3 in nss
 MOZ_OPT_FLAGS="$MOZ_OPT_FLAGS -DNSS_PKCS11_3_0_STRICT"
 
+%if !%{build_with_clang}
 %ifarch s390 %{arm} ppc aarch64 i686 x86_64 s390x
 MOZ_LINK_FLAGS="-Wl,--no-keep-memory -Wl,--reduce-memory-overheads"
 %endif
@@ -1106,6 +1111,7 @@ MOZ_LINK_FLAGS="-Wl,--no-keep-memory -Wl,--reduce-memory-overheads"
 MOZ_LINK_FLAGS="-Wl,--no-keep-memory -Wl,--strip-debug"
 echo "ac_add_options --enable-linker=gold" >> .mozconfig
 %endif
+%endif
 
 %ifarch %{arm} i686
 export RUSTFLAGS="-Cdebuginfo=0"
@@ -1116,8 +1122,20 @@ export LDFLAGS=$MOZ_LINK_FLAGS
 
 export PREFIX='%{_prefix}'
 export LIBDIR='%{_libdir}'
-export CC=gcc
-export CXX=g++
+
+%if %{build_with_clang}
+echo "export LLVM_PROFDATA=\"llvm-profdata\"" >> .mozconfig
+echo "export AR=\"llvm-ar\"" >> .mozconfig
+echo "export NM=\"llvm-nm\"" >> .mozconfig
+echo "export RANLIB=\"llvm-ranlib\"" >> .mozconfig
+echo "ac_add_options --enable-linker=lld" >> .mozconfig
+%else
+echo "export CC=gcc" >> .mozconfig
+echo "export CXX=g++" >> .mozconfig
+echo "export AR=\"gcc-ar\"" >> .mozconfig
+echo "export NM=\"gcc-nm\"" >> .mozconfig
+echo "export RANLIB=\"gcc-ranlib\"" >> .mozconfig
+%endif
 
 MOZ_SMP_FLAGS=-j1
 # More than two build tasks can lead to OOM gcc crash.