On FreeBSD, stop defaulting to MAKE=gmake

It appears that regular `make` that ships on FreeBSD 10 is compatible
enough to build Rubies. This enables ruby-build on fresh FreeBSD
installs (which don't have `gmake` by default) without having to
explicitly set `MAKE=make`.

bin/ruby-build

@@ -1032,7 +1032,7 @@ if "${CC:-cc}" -x c /dev/null -E -Wno-error=shorten-64-to-32 &>/dev/null; then
 fi
 
 if [ -z "$MAKE" ]; then
-  if [[ "FreeBSD" = "$(uname -s)" ]]; then
+  if [ "FreeBSD" = "$(uname -s)" ] && [ "$(uname -r | grep -o '[0-9]*')" -lt 10 ]; then
     export MAKE="gmake"
   else
     export MAKE="make"

test/build.bats

@@ -318,10 +318,10 @@ OUT
   assert [ -x ./here/bin/package ]
 }
 
-@test "make on FreeBSD defaults to gmake" {
+@test "make on FreeBSD 9 defaults to gmake" {
   cached_tarball "ruby-2.0.0"
 
-  stub uname "-s : echo FreeBSD"
+  stub uname "-s : echo FreeBSD" "-r : echo 9.1"
   MAKE=gmake stub_make_install
 
   MAKE= install_fixture definitions/vanilla-ruby
@@ -331,6 +331,18 @@ OUT
   unstub uname
 }
 
+@test "make on FreeBSD 10" {
+  cached_tarball "ruby-2.0.0"
+
+  stub uname "-s : echo FreeBSD" "-r : echo 10.0-RELEASE"
+  stub_make_install
+
+  MAKE= install_fixture definitions/vanilla-ruby
+  assert_success
+
+  unstub uname
+}
+
 @test "can use RUBY_CONFIGURE to apply a patch" {
   cached_tarball "ruby-2.0.0"