Repository: go
Issue: cmd/go: C compiler flags not passed when building buildid.s
Labels: NeedsFix

Please answer these questions before submitting your issue. Thanks!


### What version of Go are you using (`go version`)?
go version go1.10.3 gccgo (GCC) 8.2.1 20180813 solaris/sparc

### Does this issue reproduce with the latest release?
yes, compiled from source.

### What operating system and processor architecture are you using (`go env`)?
```
GOARCH="sparc"
GOBIN=""
GOCACHE="/home/amandeep/.cache/go-build"
GOEXE=""
GOHOSTARCH="sparc"
GOHOSTOS="solaris"
GOOS="solaris"
GOPATH="/opt/go_pkgs"
GORACE=""
GOROOT="/usr/gnu"
GOTMPDIR=""
GOTOOLDIR="/usr/gnu/libexec/gcc/sparc-sun-solaris2.11/8.2.1"
GCCGO="/usr/gnu/bin/gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build299260346=/tmp/go-build -gno-record-gcc-switches -funwind-tables"

```

### What did you do?
tried compiling a 64 bit lib with go install. In this particular example, trying to install glog

```
amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ sudo GOPATH=/opt/go_pkgs  CC='gcc -m64' CGO_CFLAGS='-m64' CGO_LDFLAGS='-m64' GOARCH=sparc64 CGO_ENABLED=1 go install -x -gccgoflags=-m64
WORK=/tmp/go-build365019570
mkdir -p $WORK/b001/
cd $WORK
/usr/gnu/bin/gccgo -fgo-importcfg=/dev/null -c -x c - || true
cd /opt/go_pkgs/src/github.com/golang/glog
/usr/gnu/bin/gccgo -c -g -fdebug-prefix-map=$WORK=/tmp/go-build -gno-record-gcc-switches -fgo-pkgpath=github.com/golang/glog -o $WORK/b001/_go_.o -I $WORK/b001/_importcfgroot_ -m64 ./glog.go ./glog_file.go
echo '  .section .go.buildid,"e"' >> $WORK/b001/_buildid.s
echo '  .byte 0x79,0x71,0x58,0x37,0x74,0x64,0x76,0x6c' >> $WORK/b001/_buildid.s
echo '  .byte 0x7a,0x59,0x53,0x39,0x41,0x6a,0x30,0x58' >> $WORK/b001/_buildid.s
echo '  .byte 0x34,0x53,0x78,0x39,0x2f,0x79,0x71,0x58' >> $WORK/b001/_buildid.s
echo '  .byte 0x37,0x74,0x64,0x76,0x6c,0x7a,0x59,0x53' >> $WORK/b001/_buildid.s
echo '  .byte 0x39,0x41,0x6a,0x30,0x58,0x34,0x53,0x78' >> $WORK/b001/_buildid.s
echo '  .byte 0x39' >> $WORK/b001/_buildid.s
echo '' >> $WORK/b001/_buildid.s
/usr/gnu/bin/gccgo -xassembler-with-cpp -I $WORK/b001/ -c -o $WORK/b001/_buildid.o -D GOOS_solaris -D GOARCH_sparc64 -D GOPKGPATH=github_com_golang_glog $WORK/b001/_buildid.s
ar rcD $WORK/b001/_pkg_.a $WORK/b001/_go_.o $WORK/b001/_buildid.o
/usr/gnu/libexec/gcc/sparc-sun-solaris2.11/8.2.1/buildid -w $WORK/b001/_pkg_.a # internal
cp $WORK/b001/_pkg_.a /root/.cache/go-build/a4/a47820a6bcb6e72c26a3be36129e80b12a0f0193dd5959e2c7304a3b169d9af8-d # internal
mkdir -p /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/
cp $WORK/b001/_pkg_.a /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a
rm -r $WORK/b001/
```

More info on the mailing list about it: https://groups.google.com/forum/#!topic/golang-nuts/mRVt7Ge2iaM

### What did you expect to see?
a 64-bit lib

### What did you see instead?
a 32-bit lib
```
amandeep@s113ldom1:/opt/go_pkgs/src/github.com/golang/glog$ file /opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a
/opt/go_pkgs/pkg/gccgo_solaris_sparc64/github.com/golang/libglog.a:     current ar archive, 32-bit symbol table
```