base: Disable Death test for fast builds

The test would otherwise fail as the expected assertion
is stripped out of the build.

Change-Id: I7c1238b43ee86ad82ad89251754e4c804d8bf16d
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/42623
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Tested-by: kokoro <noreply+kokoro@google.com>

src/base/intmath.test.cc

@@ -153,6 +153,12 @@ TEST(IntmathTest, Log2i)
  */
 TEST(IntmathDeathTest, Log2iDeath)
 {
+
+#ifdef NDEBUG
+    GTEST_SKIP() << "Skipping as assertions are "
+        "stripped out of fast builds";
+#endif
+
     // 1) value = 0
     EXPECT_DEATH({
         const int value = 0;