build: skip cgo -pie tests on freebsd-amd64.

This is a followup to http://golang.org/cl/6280.
clang -pie fails to link misc/cgo/test on freebsd-amd64.

Change-Id: I6f9575d6bb579f4d38d70707fb9c92e303e30e6f
Reviewed-on: https://go-review.googlesource.com/6520
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>

src/run.bash

@@ -158,13 +158,18 @@ android-arm | dragonfly-386 | dragonfly-amd64 | freebsd-386 | freebsd-amd64 | fr
 			go test -ldflags '-linkmode=external' ../nocgo || exit 1
 			go test -ldflags '-linkmode=external -extldflags "-static -pthread"' ../nocgo || exit 1
 		fi
-		if ! $CC -xc -o /dev/null -pie - 2>/dev/null <<<'int main() {}' ; then
-			echo "No support for -pie found, skip cgo PIE test."
-		else
-			go test -ldflags '-linkmode=external -extldflags "-pie"' || exit 1
-			go test -ldflags '-linkmode=external -extldflags "-pie"' ../testtls || exit 1
-			go test -ldflags '-linkmode=external -extldflags "-pie"' ../nocgo || exit 1
-		fi
+		case "$GOHOSTOS-$GOARCH" in
+		freebsd-amd64) ;; # clang -pie fails to link misc/cgo/test
+		*)
+			if ! $CC -xc -o /dev/null -pie - 2>/dev/null <<<'int main() {}' ; then
+				echo "No support for -pie found, skip cgo PIE test."
+			else
+				go test -ldflags '-linkmode=external -extldflags "-pie"' || exit 1
+				go test -ldflags '-linkmode=external -extldflags "-pie"' ../testtls || exit 1
+				go test -ldflags '-linkmode=external -extldflags "-pie"' ../nocgo || exit 1
+			fi
+			;;
+		esac
 		;;
 	esac
 	;;