makeBinaryWrapper: unset NIX_CFLAGS

Prevent the wrapper from being affected by the derivation's CFLAGS,
which may not even apply to GCC.

pkgs/build-support/setup-hooks/make-binary-wrapper.sh

@@ -33,6 +33,8 @@ assertExecutable() {
 # To troubleshoot a binary wrapper after you compiled it,
 # use the `strings` command or open the binary file in a text editor.
 makeWrapper() {
+    local NIX_CFLAGS_COMPILE NIX_CFLAGS_LINK
+    unset NIX_CFLAGS_COMPILE NIX_CFLAGS_LINK
     local original="$1"
     local wrapper="$2"
     shift 2