build.config.common: Revert the compiler back to clang-r370808

Due to the recent issues seen while parsing the va_args(), the compiler
is switched back to the older version,  clang-r370808, which is much
stable than the current one. Update the ABI snapshot accordingly.

Change-Id: Ib3c6b23ba40a9c036b961e839b89280aaa1cfd4e
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>