misc/cgo/testsanitizers: fix code to detect gcc version correctly

The current implementation of compilerVersion incorrectly gives an
error message that the compiler version is too old even though the
system has a recent compiler. This happens for specifically for the
gcc compiler and causes ASAN tests to be skipped.
Replacing -v with gcc dump version options seems to fix it. Running
./testsanitizers.test -test.v now shows the ASAN tests being run.
--- PASS: TestASAN (16.81s)
    --- PASS: TestASAN/asan_useAfterReturn (0.60s)
    --- PASS: TestASAN/asan_global5 (0.61s)
    --- PASS: TestASAN/asan_unsafe_fail1 (0.73s)
    --- PASS: TestASAN/asan_unsafe_fail3 (0.73s)
    --- PASS: TestASAN/asan_unsafe_fail2 (0.74s)
    --- PASS: TestASAN/asan_global4_fail (0.74s)
    --- PASS: TestASAN/asan5_fail (0.74s)
    --- PASS: TestASAN/asan3_fail (0.88s)
    --- PASS: TestASAN/asan4_fail (0.89s)
    --- PASS: TestASAN/asan2_fail (0.99s)
    --- PASS: TestASAN/asan_global3_fail (1.00s)
    --- PASS: TestASAN/asan_global1_fail (1.01s)
    --- PASS: TestASAN/asan1_fail (1.01s)
    --- PASS: TestASAN/asan_global2_fail (1.02s)
PASS

Fixes #54370

Change-Id: Iac13a1cf37de54432a6e49555f61e9ec1d781ab8
Reviewed-on: https://go-review.googlesource.com/c/go/+/422574
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Damien Neil <[email protected]>
Run-TryBot: Archana Ravindar <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>

misc/cgo/testsanitizers/cc_test.go

@@ -202,16 +202,16 @@ func compilerVersion() (version, error) {
  var match [][]byte
  if bytes.HasPrefix(out, []byte("gcc")) {
  compiler.name = "gcc"
- cmd, err := cc("-v")
+ cmd, err := cc("-dumpfullversion", "-dumpversion")
  if err != nil {
  return err
  }
- out, err := cmd.CombinedOutput()
+ out, err := cmd.Output()
  if err != nil {
  // gcc, but does not support gcc's "-v" flag?!
  return err
  }
- gccRE := regexp.MustCompile(`gcc version (\d+)\.(\d+)`)
+ gccRE := regexp.MustCompile(`(\d+)\.(\d+)`)
  match = gccRE.FindSubmatch(out)
  } else {
  clangRE := regexp.MustCompile(`clang version (\d+)\.(\d+)`)