treewide: fixup breakage due to absolute compiler path

Some packages just can't handle them #44767.  It was tempting to try
to abstract this in some way, but I didn't do that ATM.

pkgs/development/ocaml-modules/zarith/default.nix

@@ -28,7 +28,10 @@ stdenv.mkDerivation rec {
   propagatedBuildInputs = [ gmp ];
 
   patchPhase = "patchShebangs ./z_pp.pl";
+
   configurePhase = ''
+    CC=${stdenv.cc.targetPrefix}cc
+    CXX=${stdenv.cc.targetPrefix}c++
     ./configure -installdir $out/lib/ocaml/${ocaml.version}/site-lib
   '';
   preInstall = "mkdir -p $out/lib/ocaml/${ocaml.version}/site-lib";