This will help C++ code that uses exceptions to be tinier. For example,
this change shaves away 1000 lines of assembly code from LLVM's libcxx,
which is 0.7% of all assembly instructions in the entire library.
In order to improve our chances of success building other open source
projects we shouldn't define APIs that'll lead any ./configure script
astray. For example:
- brk() and sbrk() can break mac/windows support
- syscall() is a superb way to break portability
- arch_prctl() is the greatest of all horror shows
- Get mprotect_test working on aarch64
- Get completion working on python.com repl again
- Improve quality of printvideo.com and printimage.com
- Fix bug in openpty() so examples/script.c works again
