audit: fix go audit problems.

Library/Homebrew/cmd/audit.rb

@@ -399,8 +399,10 @@ class FormulaAuditor
     end
 
     # Avoid hard-coding compilers
-    if line =~ %r{(system|ENV\[.+\]\s?=)\s?['"](/usr/bin/)?(gcc|llvm-gcc|clang)['" ]}
-      problem "Use \"\#{ENV.cc}\" instead of hard-coding \"#{$3}\""
+    unless f.name == 'go' # Go needs to set CC for cgo support.
+      if line =~ %r{(system|ENV\[.+\]\s?=)\s?['"](/usr/bin/)?(gcc|llvm-gcc|clang)['" ]}
+        problem "Use \"\#{ENV.cc}\" instead of hard-coding \"#{$3}\""
+      end
     end
 
     if line =~ %r{(system|ENV\[.+\]\s?=)\s?['"](/usr/bin/)?((g|llvm-g|clang)\+\+)['" ]}