diff --git a/ninja-build.spec b/ninja-build.spec
index e21b669..6abbc91 100644
--- a/ninja-build.spec
+++ b/ninja-build.spec
@@ -33,15 +33,7 @@ fast as possible.
 %autosetup -n ninja-%{version} -p1
 
 %build
-%if 0%{?set_build_flags:1}
-%{set_build_flags}
-%else
-CFLAGS="${CFLAGS:-%optflags}" ; export CFLAGS
-CXXFLAGS="${CXXFLAGS:-%optflags}" ; export CXXFLAGS
-FFLAGS="${FFLAGS:-%optflags%{?_fmoddir: -I%_fmoddir}}" ; export FFLAGS
-FCFLAGS="${FCFLAGS:-%optflags%{?_fmoddir: -I%_fmoddir}}" ; export FCFLAGS
-%{?__global_ldflags:LDFLAGS="${LDFLAGS:-%__global_ldflags}" ; export LDFLAGS ;}
-%endif
+%set_build_flags
 %python3 configure.py --bootstrap --verbose
 ./ninja -v all
 %if %{without bootstrap}