go build: when using gccgo toolchain, please pass linker flags using -gccgoflags, not -ldflags

[dilyanpalauzov]

With gccgo, calling make produces:

CGO_ENABLED=1 GOOS=linux GOARCH=amd64 go build \
        -mod=vendor  \
        -ldflags '-X github.com/containers/podman/v3/libpod/define.gitCommit=b0d1c0fe22da27c88a0e5de11de08d63ef861347 -X github.com/containers/podman/v3/libpod/define.buildInfo=1632396554 -X github.com/containers/podman/v3/libpod/config._installPrefix=/usr/local -X github.com/containers/podman/v3/libpod/config._etcDir=/usr/local/etc ' \
        -tags " exclude_graphdriver_btrfs btrfs_noversion selinux systemd  exclude_graphdriver_devicemapper seccomp" \
        -o bin/podman ./cmd/podman
go build: when using gccgo toolchain, please pass linker flags using -gccgoflags, not -ldflags
# github.com/containers/storage/pkg/unshare
unshare.c: In function ‘parse_proc_stringlist’:
unshare.c:137:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
  137 |         for (n = 0; n < used; n++) {
      |                       ^
unshare.c:148:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Wsign-compare]
  148 |         for (n = 0; n < used; n++) {
      |                       ^
# github.com/containers/podman/v3/libpod
libpod/options.go:81:33: error: ‘copy’ defined as both imported name and global name
   81 |                                 copy(rt.storageConfig.GraphDriverOptions, config.GraphDriverOptions)
      |                                 ^
libpod/container_stat_linux.go:13:49: note: ‘copy’ imported here
   13 |         "github.com/containers/podman/v3/pkg/copy"
      |                                                 ^
make: *** [Makefile:300: bin/podman] Error 2

I would say, the first error is that -ldflags shall be replaced with -gccgoflags

[rhatdan]

Please open a PR to fix.