libc++: Disable exceptions and RTTI

Except on Mac, where exceptions are required.
And except on Android, where rtti is required.

src/buildtools/third_party/libc++/BUILD.gn

@@ -522,15 +522,11 @@ target(libcxx_target_type, "libc++") {
   # exception and rtti.
   configs -= [
     "//build/config/compiler:chromium_code",
-    "//build/config/compiler:no_exceptions",
-    "//build/config/compiler:no_rtti",
     "//build/config/coverage:default_coverage",
   ]
   configs += [
     ":config",
     "//build/config/compiler:no_chromium_code",
-    "//build/config/compiler:exceptions",
-    "//build/config/compiler:rtti",
   ]
 
   deps = [ "//third_party/llvm-libc:llvm-libc-shared" ]

src/buildtools/third_party/libc++abi/BUILD.gn

@@ -105,4 +105,35 @@ target(libcxxabi_target_type, "libc++abi") {
   # Disabling -Wexit-time-destructors, as libc++abi uses a static object for
   # at exit management (see `static DtorsManager manager`).
   configs += [ "//build/config/compiler:no_exit_time_destructors" ]
+
+  if (!is_apple) {
+    sources -= [
+      "//third_party/libc++abi/src/src/cxa_exception.cpp",
+      "//third_party/libc++abi/src/src/cxa_personality.cpp",
+      "//third_party/libc++abi/src/src/private_typeinfo.cpp",
+    ]
+    sources += [
+      "//third_party/libc++abi/src/src/cxa_noexception.cpp",
+    ]
+    defines += [ "_LIBCXXABI_NO_EXCEPTIONS" ]
+    configs -= [
+      "//build/config/compiler:exceptions",
+      "//build/config/compiler:rtti",
+    ]
+    configs += [
+      "//build/config/compiler:no_exceptions",
+      "//build/config/compiler:no_rtti",
+    ]
+  }
+  if (is_android) {
+    sources += [
+      "//third_party/libc++abi/src/src/private_typeinfo.cpp",
+    ]
+    configs -= [
+      "//build/config/compiler:no_rtti",
+    ]
+    configs += [
+      "//build/config/compiler:rtti",
+    ]
+  }
 }