crypto/x509: recently updated Xcode command line tools results in error

[bravecorvus]

What version of Go are you using (go version)?

$ go version

go version go1.12.1 darwin/amd64 (via homebrew)

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

macOS 10.14.4

go env Output

$ go env
```
GOARCH="amd64"
GOBIN="/Users/andrew/go/bin"
GOCACHE="/Users/andrew/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/andrew/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.12.1/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.12.1/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="/usr/local/bin/gcc-8"
CXX="/usr/local/bin/g++-8"
CGO_ENABLED="1"
GOMOD="/Users/andrew/Desktop/testgo/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/var/folders/2c/dff53p2915j5qx4w2vh4y47c0000gn/T/go-build680417015=/tmp/go-build -gno-record-gcc-switches -fno-common"
```

What did you do?

Switched work laptops, updated to macOS 10.14.4, installed Xcode Command Line Tools via xcode-select --install

Running a simple Hello World print out program seems to work. But doing anything else (including go get package.com/package or go build), yields errors referencing root_cgo_darwin.go.

What did you expect to see?

Nothing in particular, but standard stuff.

What did you see instead?

# crypto/x509
In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Security.framework/Headers/AuthSession.h:32,
                 from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Security.framework/Headers/Security.h:42,
                 from /usr/local/Cellar/go/1.12.1/libexec/src/crypto/x509/root_cgo_darwin.go:17:
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Security.framework/Headers/Authorization.h:193:7: error: variably modified 'bytes' at file scope
  char bytes[kAuthorizationExternalFormLength];

[bravecorvus]

[andybons]

@gilgameshskytrooper can you provide Xcode and macOS versions? Thanks.

[bravecorvus]

macOS Version: 10.14.4
XCode Version: 10.2

Thank you

[andybons]

This is a dupe of #24437

[bravecorvus]

Ahh. I see. ya, i did export CGO_ENABLED=0 and now everything works. Thanks