"This maps the -pthread option to -lpthread - this isn't 100% correct,

"This maps the -pthread option to -lpthread - this isn't 100% correct,
since handling this correctly is quite complex, and on some platforms
requires additional -D options and on some implies linking against a
different libc, but this works better than just ignoring the option.

The other change passes the -x option across to clang, which allows
compiling .c files as Objective-C and so on.  For some reason a lot of
configure scripts seem to be under the misguided impression that this
is a sensible thing to do."

Patch by David Chisnall!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@52579 91177308-0d34-0410-b5e6-96231b3b80d8