This change also fixes compilation on Linux when REACTOR_EMIT_DEBUG_INFO
is enabled, which has been broken since "-fno-exceptions" was added to
SWIFTSHADER_COMPILE_OPTIONS. Also, at some point,
LIBBACKTRACE_CONFIG_DIR stopped being used, which further broke
compiling libbacktrace.

Bug: b/145758253
Change-Id: I50f0e2c2c1dabc357dfc255a471eaf1e9fed1c2e
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/43189Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Antonio Maiorano <amaiorano@google.com>