build: Unify -logsourcelocations format

contrib/guix/libexec/build.sh

@@ -212,7 +212,6 @@ CONFIGFLAGS="-DREDUCE_EXPORTS=ON -DBUILD_BENCH=OFF -DBUILD_GUI_TESTS=OFF -DBUILD
 HOST_CFLAGS="-O2 -g"
 HOST_CFLAGS+=$(find /gnu/store -maxdepth 1 -mindepth 1 -type d -exec echo -n " -ffile-prefix-map={}=/usr" \;)
 case "$HOST" in
-    *linux*)  HOST_CFLAGS+=" -ffile-prefix-map=${DISTSRC}/src=." ;;
     *mingw*)  HOST_CFLAGS+=" -fno-ident" ;;
     *darwin*) unset HOST_CFLAGS ;;
 esac