Repeating the default WARNS here makes it slightly more difficult to
experiment with default WARNS changes, e.g. if we did something absolutely
bananas and introduced a WARNS=7 and wanted to try lifting the default to
that.
Drop most of them; there is one in the blake2 kernel module, but I suspect
it should be dropped -- the default WARNS in the rest of the build doesn't
currently apply to kernel modules, and I haven't put too much thought into
whether it makes sense to make it so.
has become very trigger-happy with libc++ 9.0.0.
It does not help that gcc's implementation of this warning is even more
trigger-happy, in the sense that it already warns on the declaration
itself, not when you are using it. This is very annoying with our use
of -Wsystem-headers. That should really be disabled for gcc.
Long story short, some of the tests were failing because they expected either
dynamic_cast or RTTI to be functional and it wasn't.
Move all common CXXFLAGS out to googletest.test.inc.mk and reference it from
googletest.test.mk and .../googletest/Makefile.inc
