This is needed when running the tests in Freestanding mode, where main()
isn't treated specially. In Freestanding, main() doesn't get mangled as
extern "C", so whatever runtime we're using fails to find the entry point.
One way to solve this problem is to define a symbol alias from __Z4mainiPPc
to _main, however this requires all definitions of main() to have the same
mangling. Hence this commit.
When statically linking libc++ on some systems, the streams are not
initialized early enough, which causes all kinds of issues. This was
reported e.g. in http://llvm.org/PR28954, but also in various open
source projects that use libc++.
Fixes http://llvm.org/PR28954.
Differential Revision: https://reviews.llvm.org/D31413
Louis Dionne