After modifying gcc.make, on Mac OSX 10.11.4 with Xcode 7.3, the build fails with this error:

Generating precompiled header precompiled.hpp.pch
In file included from <built-in>:332:
In file included from <command line>:22:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/precompiled/precompiled.hpp:30:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/asm/assembler.inline.hpp:31:
In file included from /Users/morris/hotspot/hs9/hotspot/src/cpu/x86/vm/assembler_x86.inline.hpp:30:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/code/codeCache.hpp:28:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/code/codeBlob.hpp:30:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/runtime/frame.hpp:28:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/oops/method.hpp:33:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/oops/constantPool.hpp:32:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/oops/typeArrayOop.hpp:29:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/oops/typeArrayKlass.hpp:29:
In file included from /Users/morris/hotspot/hs9/hotspot/src/share/vm/oops/arrayKlass.hpp:29:
/Users/morris/hotspot/hs9/hotspot/src/share/vm/oops/klass.hpp:327:58: error: shifting a negative signed value is undefined [-Werror,-Wshift-negative-value]
    return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);
                                ~~~~~~~~~~~~~~~~~~~~~~~~ ^
/Users/morris/hotspot/hs9/hotspot/src/share/vm/oops/klass.hpp:331:55: error: shifting a negative signed value is undefined [-Werror,-Wshift-negative-value]
    return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);
                             ~~~~~~~~~~~~~~~~~~~~~~~~ ^
2 errors generated.