[hwasan] Enable leak detection in hwasan for Fuchsia by default

[phosek]

LGTM

[leonardchan]

This was landed in fe195781ad2f1aaecd5def14f361f3590a17c79e

compiler-rt/lib/hwasan/hwasan.cpp

SetCommonFlagsDefaults();
     // FIXME: test and enable.
     cf.check_printf = false;
     cf.intercept_tls_get_addr = true;
     cf.exitcode = 99;
     // 8 shadow pages ~512kB, small enough to cover common stack sizes.
     cf.clear_shadow_mmap_threshold = 4096 * (SANITIZER_ANDROID ? 2 : 8);
     // Sigtrap is used in error reporting.
     cf.handle_sigtrap = kHandleSignalExclusive;
-    // For now only tested on Linux. Other plantforms can be turned on as they
-    // become ready.
-    cf.detect_leaks = cf.detect_leaks && SANITIZER_LINUX && !SANITIZER_ANDROID;
+    // For now only tested on Linux and Fuchsia. Other plantforms can be turned
+    // on as they become ready.
+    constexpr bool can_detect_leaks =
+        (SANITIZER_LINUX && !SANITIZER_ANDROID) || SANITIZER_FUCHSIA;
+    cf.detect_leaks = cf.detect_leaks && can_detect_leaks;
 
 #if SANITIZER_ANDROID
     // Let platform handle other signals. It is better at reporting them then we
     // are.
     cf.handle_segv = kHandleSignalNo;
     cf.handle_sigbus = kHandleSignalNo;
     cf.handle_abort = kHandleSignalNo;
     cf.handle_sigill = kHandleSignalNo;