Not all platforms accept -stdlib or -rtlib. Instead of complaining about
the wrong argument to these options, clang complains about the option
itself being present.
Pass an appropriate -target to the clang invocations.
Since ToolChain::GetCXXStdlibType() is a simple getter that might emit
the "invalid library name in argument" warning, it can conceivably be
called several times while initializing the build pipeline.
Before this patch, a simple 'clang++ -stdlib=foo ./test.cpp' would print
the warning twice, -rt=lib=foo would print 6 times.
Change this and always only print the warning once. Keep the rest of the
semantics of the functions.
Differential Revision: https://reviews.llvm.org/D95915
Nico Weber