Move selection of C++ STL into the build system.

Preparing for migration from stlport to libc++. STL selection is done
with LOCAL_CXX_STL (valid values are default, none, libc++,
libc++_static, stlport, stlport_static, bionic).

The selection of the STL is as follows:

    if LOCAL_CXX_STL == 'default'
      ifdef LOCAL_SDK_VERSION
        Use whatever STL the other NDK options have selected.
      else
        Use bionic's libstdc++ for target, GNU libstdc++ for host. This
        is compatible with the existing build options.
      endif
    else
      if LOCAL_CXX_STL == 'stlport'
        Use stlport.
      else if LOCAL_CXX_STL == 'libc++'
        Use libc++.
      else if LOCAL_CXX_STL == ''
        Don't use any STL.
      endif
    endif

Bug: 15193147
Change-Id: If712ba0ae7908d8147a69e29da5c453a183d6540
diff --git a/core/binary.mk b/core/binary.mk
index 60cd4c6..936b429 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -107,6 +107,7 @@
 my_cflags := $(LOCAL_CFLAGS)
 my_cppflags := $(LOCAL_CPPFLAGS)
 my_ldflags := $(LOCAL_LDFLAGS)
+my_ldlibs := $(LOCAL_LDLIBS)
 my_asflags := $(LOCAL_ASFLAGS)
 my_cc := $(LOCAL_CC)
 my_cxx := $(LOCAL_CXX)
@@ -164,11 +165,66 @@
 
 my_cflags := $(filter-out $($(LOCAL_2ND_ARCH_VAR_PREFIX)$(my_prefix)GLOBAL_UNSUPPORTED_CFLAGS),$(my_cflags))
 
+# Only around for development purposes. Will be removed soon.
+my_libcxx_is_default := false
 
-# Replace libstdc++ with libc++ if it's seen
-my_libcxx := $(filter libc++, $(my_shared_libraries))
-ifdef my_libcxx
-my_system_shared_libraries := $(filter-out libstdc++, $(my_system_shared_libraries))
+# Select the appropriate C++ STL
+ifeq ($(strip $(LOCAL_CXX_STL)),default)
+    ifndef LOCAL_SDK_VERSION
+        ifeq ($(strip $(my_libcxx_is_default)),true)
+            # Platform code. Select the appropriate STL.
+            my_cxx_stl := libc++
+        else
+            my_cxx_stl := bionic
+        endif
+    else
+        my_cxx_stl := ndk
+    endif
+else
+    my_cxx_stl := $(strip $(LOCAL_CXX_STL))
+endif
+
+ifneq ($(filter $(my_cxx_stl),libc++ libc++_static),)
+    my_cflags += -D_USING_LIBCXX
+    my_c_includes += external/libcxx/include
+    ifeq ($(my_cxx_stl),libc++)
+        my_shared_libraries += libc++
+    else
+        my_static_libraries += libc++_static
+    endif
+
+    ifdef LOCAL_IS_HOST_MODULE
+        my_cppflags += -nostdinc++
+        my_ldflags += -nodefaultlibs
+        my_ldlibs += -lc -lm
+    endif
+else ifneq ($(filter $(my_cxx_stl),stlport stlport_static),)
+    my_c_includes += external/stlport/stlport bionic/libstdc++/include bionic
+    ifeq ($(my_cxx_stl),stlport)
+        my_shared_libraries += libstdc++ libstlport
+    else
+        my_static_libraries += libstdc++ libstlport_static
+    endif
+else ifeq ($(my_cxx_stl),ndk)
+    # Using an NDK STL. Handled farther up in this file.
+    ifndef LOCAL_IS_HOST_MODULE
+        my_system_shared_libraries += libstdc++
+    endif
+else ifeq ($(my_cxx_stl),bionic)
+    # Using bionic's basic libstdc++. Not actually an STL. Only around until the
+    # tree is in good enough shape to not need it.
+    ifndef LOCAL_IS_HOST_MODULE
+        my_c_includes += bionic/libstdc++/include
+        my_system_shared_libraries += libstdc++
+    endif
+    # Host builds will use GNU libstdc++.
+else ifeq ($(my_cxx_stl),none)
+    ifdef LOCAL_IS_HOST_MODULE
+        my_cppflags += -nostdinc++
+        my_ldflags += -nodefaultlibs -lc -lm
+    endif
+else
+    $(error $(my_cxx_stl) is not a supported STL.)
 endif
 
 # Add static HAL libraries
@@ -947,7 +1003,7 @@
 $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_C_INCLUDES := $(my_c_includes)
 $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_IMPORT_INCLUDES := $(import_includes)
 $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_LDFLAGS := $(my_ldflags)
-$(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_LDLIBS := $(LOCAL_LDLIBS)
+$(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_LDLIBS := $(my_ldlibs)
 $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_NO_CRT := $(strip $(LOCAL_NO_CRT) $(LOCAL_NO_CRT_$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH)))
 $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_LIBCXX := $(my_libcxx)