go: only set CC when cross-compiling

This avoids he default CC for cgo being hardcoded, when we only want to
overwrite it during compilation.

pkgs/development/compilers/go/1.13.nix

@@ -186,8 +186,11 @@ stdenv.mkDerivation rec {
 
     export PATH=$(pwd)/bin:$PATH
 
+    ${optionalString (stdenv.buildPlatform != stdenv.targetPlatform) ''
     # Independent from host/target, CC should produce code for the building system.
+    # We only set it when cross-compiling.
     export CC=${buildPackages.stdenv.cc}/bin/cc
+    ''}
     ulimit -a
   '';
 

pkgs/development/compilers/go/1.14.nix

@@ -193,8 +193,11 @@ stdenv.mkDerivation rec {
 
     export PATH=$(pwd)/bin:$PATH
 
+    ${optionalString (stdenv.buildPlatform != stdenv.targetPlatform) ''
     # Independent from host/target, CC should produce code for the building system.
+    # We only set it when cross-compiling.
     export CC=${buildPackages.stdenv.cc}/bin/cc
+    ''}
     ulimit -a
   '';