[scudo][standalone] Enable death tests on Fuchsia

zxtest doesn't have `EXPECT_DEATH` and the Scudo unit-tests were
defining it as a no-op.

This enables death tests on Fuchsia by using `ASSERT_DEATH` instead.
I used a lambda to wrap the expressions as this appears to not be
working the same way as `EXPECT_DEATH`.

Additionnally, a death test using `alarm` was failing with the change,
as it's currently not implemented in Fuchsia, so move that test within
a `!SCUDO_FUCHSIA` block.

Differential Revision: https://reviews.llvm.org/D94362

Author: Kostya Kortchinsky

compiler-rt/lib/scudo/standalone/tests/scudo_unit_test.h

@@ -16,10 +16,15 @@
 
 // If EXPECT_DEATH isn't defined, make it a no-op.
 #ifndef EXPECT_DEATH
+// If ASSERT_DEATH is defined, make EXPECT_DEATH a wrapper to it.
+#ifdef ASSERT_DEATH
+#define EXPECT_DEATH(X, Y) ASSERT_DEATH(([&] { X; }), "")
+#else
 #define EXPECT_DEATH(X, Y)                                                     \
   do {                                                                         \
   } while (0)
-#endif
+#endif // ASSERT_DEATH
+#endif // EXPECT_DEATH
 
 // If EXPECT_STREQ isn't defined, define our own simple one.
 #ifndef EXPECT_STREQ

compiler-rt/lib/scudo/standalone/tests/wrappers_c_test.cpp

@@ -303,8 +303,10 @@ TEST(ScudoWrappersCTest, MallocIterateBoundary) {
   }
 }
 
-// We expect heap operations within a disable/enable scope to deadlock.
+// Fuchsia doesn't have alarm, fork or malloc_info.
+#if !SCUDO_FUCHSIA
 TEST(ScudoWrappersCTest, MallocDisableDeadlock) {
+  // We expect heap operations within a disable/enable scope to deadlock.
   EXPECT_DEATH(
       {
         void *P = malloc(Size);
@@ -318,9 +320,6 @@ TEST(ScudoWrappersCTest, MallocDisableDeadlock) {
       "");
 }
 
-// Fuchsia doesn't have fork or malloc_info.
-#if !SCUDO_FUCHSIA
-
 TEST(ScudoWrappersCTest, MallocInfo) {
   // Use volatile so that the allocations don't get optimized away.
   void *volatile P1 = malloc(1234);