gcc and clang should use the same ld flags

If I build openjdk with clang, I see:

"""
OpenJDK 64-Bit Server VM warning: You have loaded library ...build/linux-x86_64-normal-server-release/jdk/lib/server/libjvm.so which might have disabled stack guard. The VM will try to fix the stack guard now.
It's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'.
OpenJDK 64-Bit Server VM warning: Unable to fix stack guard. Giving up.
"""

in general, gcc and clang should treat all linker flags the same, especially given that clang tries hard to be gcc-compatible. E.g. -z relro