On Linux __libc_longjmp is called from pthread_exit, and uses a
jmp_buf that was initialized by _setjmp called from
__libc_start_main. The _setjmp call does not use the PLT, so we
cannot intercept it.
The result is a mismatch in jmp_buf format, since _setjmp uses
glibc's format while our __libc_longjmp interceptor uses HWASan's
format. Removing the __libc_longjmp interceptor avoids the mismatch.
See discussion on https://reviews.llvm.org/D69045.