dump stack trace in FM on failure

In CrashHandler...
  - make CrashHandler a non-noop... don't know why it's disabled
  - fix bitrot since we last built it
  - update to demangle symbols on Linux too, not just Mac
  - catch SIGTRAP, which will catch SK_ABORT / SkASSERT,
    unless otherwise hooked (e.g. by a debugger)

In fm...
  - use CrashHandler
  - convert exit_with_failure to SK_ABORT so they'll also dump a trace
  - flush stdout after printing what's running

Change-Id: Ib20d0e4f442d73c28e193396dc6e85935fc58544
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/208151
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 9faf14d..61715a7 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1654,7 +1654,10 @@
     if (is_ios) {
       sources += [ "tools/ios_utils.m" ]
       libs += [ "Foundation.framework" ]
+    } else if (is_win) {
+      libs += [ "DbgHelp.lib" ]
     }
+
     defines = []
     if (skia_tools_require_resources) {
       defines += [ "SK_TOOLS_REQUIRE_RESOURCES" ]