syscall: don't assume we have a GETEUID system call

On Alpha GNU/Linux there is no geteuid system call, there is only
getresuid.  The raw geteuid system call is only used for testing, so
just skip the test if it's not available.

Change-Id: I2cc972da32d56767f61c8c6f4fa1872f74545c82
Reviewed-on: https://go-review.googlesource.com/137655
Reviewed-by: Cherry Zhang <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>

Author: ianlancetaylor

libgo/go/syscall/syscall_linux_test.go

@@ -302,6 +302,10 @@ func TestSyscallNoError(t *testing.T) {
 		t.Skip("skipping root only test")
 	}
 
+	if syscall.Sys_GETEUID == 0 {
+		t.Skip("skipping because there is no geteuid system call")
+	}
+
 	// Copy the test binary to a location that a non-root user can read/execute
 	// after we drop privileges
 	tempDir, err := ioutil.TempDir("", "TestSyscallNoError")

libgo/mksysinfo.sh

@@ -138,6 +138,12 @@ if ! grep '^const SYS_GETDENTS64 ' ${OUT} >/dev/null 2>&1; then
   echo "const SYS_GETDENTS64 = 0" >> ${OUT}
 fi
 
+# The syscall package wants the geteuid system call number.  It isn't
+# defined on Alpha, which only provides the getresuid system call.
+if ! grep '^const SYS_GETEUID ' ${OUT} >/dev/null 2>&1; then
+  echo "const SYS_GETEUID = 0" >> ${OUT}
+fi
+
 # Stat constants.
 grep '^const _S_' gen-sysinfo.go | \
   sed -e 's/^\(const \)_\(S_[^= ]*\)\(.*\)$/\1\2 = _\2/' >> ${OUT}