Warn when using msan on Android

Msan is not supported on Android as mentioned in google/sanitizers#1381.
We proactively give the warning saying it is unsupported to fix android/ndk#1958.

Author: Sharjeel-Khan

clang/lib/Driver/SanitizerArgs.cpp

@@ -530,6 +530,16 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
       }
       Add &= Supported;
 
+      // Msan is not supported on Android
+      if ((Add & SanitizerKind::Memory) && TC.getTriple().isAndroid()) {
+        if (DiagnoseErrors) {
+          D.Diag(diag::warn_drv_unsupported_option_for_target)
+                  << "-fsanitize=memory" << Triple.str();
+        }
+        DiagnosedKinds |= SanitizerKind::Memory;
+        Add &= ~SanitizerKind::Memory;
+      }
+
       // Test for -fno-rtti + explicit -fsanitizer=vptr before expanding groups
       // so we don't error out if -fno-rtti and -fsanitize=undefined were
       // passed.

clang/test/Driver/fsanitize.c

@@ -399,6 +399,11 @@
 // RUN: %clang --target=arm-linux-androideabi %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ANDROID-NO-ASAN
 // CHECK-ANDROID-NO-ASAN: "-mrelocation-model" "pic"
 
+// RUN: %clang --target=aarch64-linux-android -fsanitize=memory %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-MSAN-ANDROID
+// RUN: %clang --target=i386-linux-android -fsanitize=memory %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-MSAN-ANDROID
+// RUN: %clang --target=x86_64-linux-android -fsanitize=memory %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-MSAN-ANDROID
+// CHECK-MSAN-ANDROID: ignoring '-fsanitize=memory' option as it is not currently supported for target
+
 // RUN: %clang --target=x86_64-linux-gnu %s -fsanitize=undefined -### 2>&1 | FileCheck %s --check-prefix=CHECK-RECOVER-UBSAN
 // RUN: %clang --target=x86_64-linux-gnu %s -fsanitize=undefined -fsanitize-recover -### 2>&1 | FileCheck %s --check-prefix=CHECK-RECOVER-UBSAN
 // RUN: %clang --target=x86_64-linux-gnu %s -fsanitize=undefined -fsanitize-recover=all -### 2>&1 | FileCheck %s --check-prefix=CHECK-RECOVER-UBSAN