Add Android.mk to aid integration with FirefoxOS

This Android.mk is part of "Bug 831147 - Integrate apitrace into build"
https://bugzilla.mozilla.org/831147
With this addition, when apitrace sources are cloned into
B2GROOT/external/apitrace, then the FirefoxOS build system picks
up automatically apitrace, compiles and install is to the right place.

Android.mk

@@ -0,0 +1,85 @@
+#
+# This file helps integrate apitrace into FirefoxOS - when apitrace
+# sources are put in B2GROOT/external/apitrace (including this Android.mk
+# file), then the B2G build system will pick apitrace automatically and
+# compile and install it into the system images seamlessly.
+#
+
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+
+LOCAL_MODULE := egltrace
+LOCAL_MODULE_TAGS := debug eng
+
+include $(BUILD_SHARED_LIBRARY)
+
+# Below we hook the whole process of configuring and compiling apitrace,
+# described in INSTALL.markdown. We override the
+# $(linked_module): targed, which is already defined by
+# $(BUILD_SHARED_LIBRARY) - by default it would want to compile the
+# library out of some source files.
+# We also override the target $(LOCAL_INSTALLED_MODULE): which installs
+# the shared library because we want it installed in
+# /lib/apitrace/wrappers/egltrace.so instead of /lib/egltrace.so because
+# /bin/apitrace searches for the library in that directory.
+# The rules will end up with /lib/apitrace/wrappers/egltrace.so and
+# /bin/apitrace inside system.img.
+MY_APITRACE_ROOT := $(TOPDIR)external/apitrace
+MY_APITRACE_BUILD_ROOT_HOST := out/host/apitrace
+MY_APITRACE_BUILD_ROOT_TARGET := out/target/apitrace
+MY_APITRACE_NDK_BZ2 := android-ndk-r8-linux-x86.tar.bz2
+MY_APITRACE_NDK := android-ndk-r8
+
+apitrace_private_target:
+	$(hide) # apitrace: run cmake for the host if it has not been run
+	$(hide) if [ ! -e $(MY_APITRACE_BUILD_ROOT_HOST)/Makefile ] ; then \
+		cd $(MY_APITRACE_ROOT) && \
+		cmake -H. -B../../$(MY_APITRACE_BUILD_ROOT_HOST) ; \
+	fi
+	$(hide) # apitrace: compile for the host
+	$(hide) make -C $(MY_APITRACE_BUILD_ROOT_HOST)
+	$(hide) # apitrace: download NDK archive if it is not present
+	$(hide) if [ ! -e $(MY_APITRACE_ROOT)/$(MY_APITRACE_NDK_BZ2) ] ; then \
+		cd $(MY_APITRACE_ROOT) && \
+		curl -O http://dl.google.com/android/ndk/$(MY_APITRACE_NDK_BZ2) ; \
+	fi
+	$(hide) # apitrace: extract NDK archive if it is not extracted
+	$(hide) if [ ! -e $(MY_APITRACE_ROOT)/$(MY_APITRACE_NDK) ] ; then \
+		cd $(MY_APITRACE_ROOT) && \
+		tar -jxf $(MY_APITRACE_NDK_BZ2) ; \
+	fi
+	$(hide) # apitrace: run cmake for android if it has not been run
+	$(hide) if [ ! -e $(MY_APITRACE_BUILD_ROOT_TARGET)/Makefile ] ; then \
+		cd $(MY_APITRACE_ROOT) && \
+		ANDROID_NDK=$(MY_APITRACE_NDK) \
+		cmake \
+		-DCMAKE_TOOLCHAIN_FILE=cmake/toolchain/android.toolchain.cmake \
+		-DANDROID_API_LEVEL=9 -H. -B../../$(MY_APITRACE_BUILD_ROOT_TARGET) ; \
+	fi
+	$(hide) # apitrace: compile for android
+	$(hide) make -C $(MY_APITRACE_BUILD_ROOT_TARGET)
+
+$(linked_module): apitrace_private_target
+	$(hide) # apitrace: copy egltrace lib to where the build system expects it
+	$(hide) mkdir -p $(dir $@)
+	$(hide) cp $(MY_APITRACE_BUILD_ROOT_TARGET)/wrappers/egltrace$(TARGET_SHLIB_SUFFIX) $@
+
+$(LOCAL_INSTALLED_MODULE): $(LOCAL_BUILT_MODULE) | $(ACP)
+	@echo "Install (overridden): $@"
+	@mkdir -p $(dir $@)/apitrace/wrappers
+	$(hide) $(ACP) -fp $< $(dir $@)/apitrace/wrappers/egltrace$(TARGET_SHLIB_SUFFIX)
+
+#
+
+include $(CLEAR_VARS)
+
+LOCAL_MODULE := apitrace
+LOCAL_MODULE_TAGS := debug eng
+
+include $(BUILD_EXECUTABLE)
+
+$(linked_module): apitrace_private_target
+	$(hide) # apitrace: copy apitrace executable to where the build system expects it
+	$(hide) mkdir -p $(dir $@)
+	$(hide) cp $(MY_APITRACE_BUILD_ROOT_TARGET)/apitrace$(TARGET_EXECUTABLE_SUFFIX) $@