[trap-handler] Add missing newlines

If trap handlers cannot be installed, we printed two lines to stdout
and stderr, both not terminated by a newline. This CL adds a newline to
one output and uses the FATAL macro for the other, highlighting the
error better and showing the location where it happens.

R=eholk@chromium.org

Bug: v8:7570
Change-Id: Ic24f48f92b87528e0fd5889badf2c90d765e451a
Reviewed-on: https://chromium-review.googlesource.com/1047606Reviewed-by: Eric Holk <eholk@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53043}

src/d8.cc

@@ -3320,8 +3320,7 @@ int Shell::Main(int argc, char* argv[]) {
   if (V8_TRAP_HANDLER_SUPPORTED && i::FLAG_wasm_trap_handler) {
     constexpr bool use_default_trap_handler = true;
     if (!v8::V8::EnableWebAssemblyTrapHandler(use_default_trap_handler)) {
-      fprintf(stderr, "Could not register trap handler");
-      exit(1);
+      FATAL("Could not register trap handler");
     }
   }
 

src/trap-handler/handler-outside-linux.cc

@@ -58,7 +58,7 @@ bool RegisterDefaultTrapHandler() {
   if (installed_handler.sa_sigaction != HandleSignal) {
     printf(
         "WARNING: sanitizers are preventing signal handler installation. "
-        "Trap handlers are disabled.");
+        "Trap handlers are disabled.\n");
     return false;
   }
 #endif