Android: Record use of C++ by static libs in exported Android.mk files

When a `PREBUILT_STATIC_LIBRARY` uses C++ in its sources then the `.a`
file will have a link-time dependency on the C++ runtime libraries.
Android NDK r14 will add a way to give this information to the NDK build
system by adding a `LOCAL_HAS_CPP` setting to the `Android.mk` file.
Add this for exported static libraries that use C++.

Source/cmExportBuildAndroidMKGenerator.cxx

@@ -9,6 +9,8 @@
 #include "cmMakefile.h"
 #include "cmTargetExport.h"
 
+#include <algorithm>
+
 cmExportBuildAndroidMKGenerator::cmExportBuildAndroidMKGenerator()
 {
   this->LG = CM_NULLPTR;
@@ -164,6 +166,16 @@ void cmExportBuildAndroidMKGenerator::GenerateInterfaceProperties(
       }
     }
   }
+
+  // Tell the NDK build system if prebuilt static libraries use C++.
+  if (target->GetType() == cmState::STATIC_LIBRARY) {
+    cmLinkImplementation const* li = target->GetLinkImplementation(config);
+    if (std::find(li->Languages.begin(), li->Languages.end(), "CXX") !=
+        li->Languages.end()) {
+      os << "LOCAL_HAS_CPP := true\n";
+    }
+  }
+
   switch (target->GetType()) {
     case cmState::SHARED_LIBRARY:
     case cmState::MODULE_LIBRARY:

Tests/RunCMake/AndroidMK/AndroidMK.cmake

@@ -2,7 +2,7 @@ project(build)
 set(CMAKE_BUILD_TYPE Debug)
 add_library(foo foo.cxx)
 add_library(car foo.cxx)
-add_library(bar  foo.cxx)
+add_library(bar bar.c)
 add_library(dog  foo.cxx)
 target_link_libraries(foo car bar dog debug -lm)
 export(TARGETS bar dog car foo  ANDROID_MK

Tests/RunCMake/AndroidMK/bar.c

@@ -0,0 +1,3 @@
+void bar(void)
+{
+}

Tests/RunCMake/AndroidMK/expectedBuildAndroidMK.txt

@@ -7,11 +7,13 @@ include.*PREBUILT_STATIC_LIBRARY.*
 include.*CLEAR_VARS.*
 LOCAL_MODULE.*dog
 LOCAL_SRC_FILES.*.*dog.*
+LOCAL_HAS_CPP := true
 include.*PREBUILT_STATIC_LIBRARY.*
 .*
 include.*CLEAR_VARS.*
 LOCAL_MODULE.*car
 LOCAL_SRC_FILES.*.*car.*
+LOCAL_HAS_CPP := true
 include.*PREBUILT_STATIC_LIBRARY.*
 .*
 include.*CLEAR_VARS.*
@@ -20,4 +22,5 @@ LOCAL_SRC_FILES.*.*foo.*
 LOCAL_CPP_FEATURES.*rtti exceptions
 LOCAL_STATIC_LIBRARIES.*car bar dog
 LOCAL_EXPORT_LDLIBS := -lm
+LOCAL_HAS_CPP := true
 include.*PREBUILT_STATIC_LIBRARY.*

Tests/RunCMake/AndroidMK/expectedInstallAndroidMK.txt

@@ -9,11 +9,13 @@ include.*PREBUILT_STATIC_LIBRARY.*
 include.*CLEAR_VARS.
 LOCAL_MODULE.*dog
 LOCAL_SRC_FILES.*_IMPORT_PREFIX./lib.*dog.*
+LOCAL_HAS_CPP := true
 include.*PREBUILT_STATIC_LIBRARY.*
 
 include.*CLEAR_VARS.*
 LOCAL_MODULE.*car
 LOCAL_SRC_FILES.*_IMPORT_PREFIX./lib.*car.*
+LOCAL_HAS_CPP := true
 include.*PREBUILT_STATIC_LIBRARY.*
 
 include.*CLEAR_VARS.*
@@ -22,4 +24,5 @@ LOCAL_SRC_FILES.*_IMPORT_PREFIX\)/lib.*foo.*
 LOCAL_CPP_FEATURES.*rtti exceptions
 LOCAL_STATIC_LIBRARIES.*car bar dog
 LOCAL_EXPORT_LDLIBS := -lm
+LOCAL_HAS_CPP := true
 include.*PREBUILT_STATIC_LIBRARY.*