Revert "Revert "Merge pull request #28029 from cstrahan/hardening-fix""

This reverts commit 6c064e6b1f, reapplying
PR #28029 which was supposed to have gone to staging all along.

pkgs/build-support/cc-wrapper/cc-wrapper.sh

@@ -134,8 +134,8 @@ fi
 source @out@/nix-support/add-hardening.sh
 
 # Add the flags for the C compiler proper.
-extraAfter=($NIX_@infixSalt@_CFLAGS_COMPILE "${hardeningCFlags[@]}")
-extraBefore=()
+extraAfter=($NIX_@infixSalt@_CFLAGS_COMPILE)
+extraBefore=(${hardeningCFlags[@]+"${hardeningCFlags[@]}"})
 
 if [ "$dontLink" != 1 ]; then