MB-47145: Only install signal handler on x86

The signal handler code in forestDB is x86-specific. Don't install it
on non-x86 architectures; relying on whatever higher-level signal
handlers the application has (Breakpad etc).

Change-Id: I0b9c5f15f898ab636802b833f9f5e1f1012cf4da
Reviewed-on: http://review.couchbase.org/c/forestdb/+/156528
Reviewed-by: Chris Hillery <[email protected]>
Tested-by: Build Bot <[email protected]>

Author: daverigby

utils/debug.cc

@@ -69,7 +69,8 @@ static void _dbg_hang_process(void)
 
 // to profile first install perf
 // echo 0 > /proc/sys/kernel/kptr_restrict
-#if defined(__linux__) && !defined(__ANDROID__)
+#if defined(__linux__) && !defined(__ANDROID__) && \
+        (defined(__i386__) || defined(__x86_64__))
 #include <string.h>
 #include <dlfcn.h>
 #include <ucontext.h>