hack: name for target ARM architecture not specified

Builds currently doesn't set the right name for target ARM
architecture through switches in CGO_CFLAGS and CGO_CXXFLAGS
when doing cross-compilation. This was previously fixed in moby#43474

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

Author: crazy-max

hack/make/.binary

@@ -18,7 +18,8 @@ source "${MAKEDIR}/.go-autogen"
 
 	case "$(go env GOOS)/$(go env GOARCH)" in
 		linux/arm)
-			case "${GOARM}" in
+			# specify name of the target ARM architecture for cross-compilation
+			case "$(go env GOARM)" in
 				5)
 					export CGO_CFLAGS="-march=armv5t"
 					export CGO_CXXFLAGS="-march=armv5t"