This commit adds new compiler options -no-warning-as-error/-warning-as-error which allows users to specify behavior for exact warnings and warning groups.
swift-compatibility-symbols, swift-def-to-strings-converter,
and swift-serialize-diagnostics don't use any Swift modules. But when
SWIFT_SWIFT_PARSER was enabled, they are linked with swiftCore. But
these binaries can be executed before the runtime is being built.
We need to stop them linking with swiftCore.
In Linux. Instead of setting temporary "fallback" RUNPATH, Set
LD_LIBRARY_PATH to builder's runtime when building standard library.
So we don't need to strip the temporary RUNPATH when installing.
