cmd/cgo: use -Wl,--no-gc-sections if available

This change adds `--no-gc-sections` to the external linker if the flag
is understood.

zig cc passes `--gc-sections` to the underlying linker, which then
causes undefined symbol errors when compiling with cgo but without C
code. Minimal example:

**main.go**
```
package main
import _ "runtime/cgo"
func main() {}
```

Run (works after the patch, doesn't work before):

```
CC="zig cc" go build main.go
```

Among the existing code, `src/runtime/testdata/testprognet` fails too:
```
src/runtime/testdata/testprognet$ CC="zig cc" go build .
net(.text): relocation target __errno_location not defined
net(.text): relocation target getaddrinfo not defined
net(.text): relocation target freeaddrinfo not defined
net(.text): relocation target gai_strerror not defined
runtime/cgo(.text): relocation target stderr not defined
runtime/cgo(.text): relocation target fwrite not defined
runtime/cgo(.text): relocation target vfprintf not defined
runtime/cgo(.text): relocation target fputc not defined
runtime/cgo(.text): relocation target abort not defined
runtime/cgo(.text): relocation target pthread_create not defined
runtime/cgo(.text): relocation target nanosleep not defined
runtime/cgo(.text): relocation target pthread_detach not defined
runtime/cgo(.text): relocation target stderr not defined
runtime/cgo(.text): relocation target strerror not defined
runtime/cgo(.text): relocation target fprintf not defined
runtime/cgo(.text): relocation target abort not defined
runtime/cgo(.text): relocation target pthread_mutex_lock not defined
runtime/cgo(.text): relocation target pthread_cond_wait not defined
runtime/cgo(.text): relocation target pthread_mutex_unlock not defined
runtime/cgo(.text): relocation target pthread_cond_broadcast not defined
runtime/cgo(.text): relocation target malloc not defined
```

With the patch both examples build as expected.

@ianlancetaylor suggested:

> It would be fine with me if somebody wants to send a cgo patch that
passes -Wl,--no-gc-sections, with a fallback if that option is not
supported.

... and this is what we are doing. Tested with zig
0.10.0-dev.2252+a4369918b

Fixes #52690

Author: motiejus

src/cmd/go/internal/work/exec.go

@@ -2528,6 +2528,13 @@ func (b *Builder) compilerCmd(compiler []string, incdir, workdir string) []strin
 		a = append(a, "-Qunused-arguments")
 	}
 
+	// zig cc passes --gc-sections to the underlying linker, which then causes
+	// undefined symbol errors when compiling with cgo but without C code.
+	// https://github.com/golang/go/issues/52690
+	if b.gccSupportsLinkerFlag(compiler, "-Wl,--no-gc-sections") {
+		a = append(a, "-Wl,--no-gc-sections")
+	}
+
 	// disable word wrapping in error messages
 	a = append(a, "-fmessage-length=0")