Merge pull request #13939 from komakai:android-build-improvements

* Android build improvements
* look for NDK in "ndk-bundle" directory under the SDK directory if location not specified
* look for cmake and ninja in "cmake" directory under the SDK directory if not found in the path
* disable use of ccache if not found in the path

* Redo build tool existence checks

platforms/android/build_sdk.py

@@ -48,6 +48,16 @@ def check_dir(d, create=False, clean=False):
             os.makedirs(d)
     return d
 
+def check_executable(cmd):
+    try:
+        FNULL = open(os.devnull, 'w')
+        retcode = subprocess.call(cmd, stdout=FNULL, stderr=subprocess.STDOUT)
+        if retcode < 0:
+            return False
+        return True
+    except:
+        return False
+
 def determine_opencv_version(version_hpp_path):
     # version in 2.4 - CV_VERSION_EPOCH.CV_VERSION_MAJOR.CV_VERSION_MINOR.CV_VERSION_REVISION
     # version in master - CV_VERSION_MAJOR.CV_VERSION_MINOR.CV_VERSION_REVISION-CV_VERSION_STATUS
@@ -131,6 +141,36 @@ class Builder:
         self.opencv_version = determine_opencv_version(os.path.join(self.opencvdir, "modules", "core", "include", "opencv2", "core", "version.hpp"))
         self.use_ccache = False if config.no_ccache else True
 
+    def get_cmake(self):
+        if check_executable(['cmake', '--version']):
+            log.info("Using cmake from PATH")
+            return 'cmake'
+        # look to see if Android SDK's cmake is installed
+        android_cmake = os.path.join(os.environ['ANDROID_SDK'], 'cmake')
+        if os.path.exists(android_cmake):
+            cmake_subdirs = [f for f in os.listdir(android_cmake) if check_executable([os.path.join(android_cmake, f, 'bin', 'cmake'), '--version'])]
+            if len(cmake_subdirs) > 0:
+                # there could be more than one - just take the first one
+                cmake_from_sdk = os.path.join(android_cmake, cmake_subdirs[0], 'bin', 'cmake')
+                log.info("Using cmake from Android SDK: %s", cmake_from_sdk)
+                return cmake_from_sdk
+        raise Fail("Can't find cmake")
+
+    def get_ninja(self):
+        if check_executable(['ninja', '--version']):
+            log.info("Using ninja from PATH")
+            return 'ninja'
+        # Android SDK's cmake includes a copy of ninja - look to see if its there
+        android_cmake = os.path.join(os.environ['ANDROID_SDK'], 'cmake')
+        if os.path.exists(android_cmake):
+            cmake_subdirs = [f for f in os.listdir(android_cmake) if check_executable([os.path.join(android_cmake, f, 'bin', 'ninja'), '--version'])]
+            if len(cmake_subdirs) > 0:
+                # there could be more than one - just take the first one
+                ninja_from_sdk = os.path.join(android_cmake, cmake_subdirs[0], 'bin', 'ninja')
+                log.info("Using ninja from Android SDK: %s", ninja_from_sdk)
+                return ninja_from_sdk
+        raise Fail("Can't find ninja")
+
     def get_toolchain_file(self):
         if not self.config.force_opencv_toolchain:
             toolchain = os.path.join(os.environ['ANDROID_NDK'], 'build', 'cmake', 'android.toolchain.cmake')
@@ -155,7 +195,7 @@ class Builder:
             rm_one(d)
 
     def build_library(self, abi, do_install):
-        cmd = ["cmake", "-GNinja"]
+        cmd = [self.get_cmake(), "-GNinja"]
         cmake_vars = dict(
             CMAKE_TOOLCHAIN_FILE=self.get_toolchain_file(),
             INSTALL_CREATE_DISTRIB="ON",
@@ -168,6 +208,7 @@ class Builder:
             BUILD_DOCS="OFF",
             BUILD_ANDROID_EXAMPLES="ON",
             INSTALL_ANDROID_EXAMPLES="ON",
+            CMAKE_MAKE_PROGRAM=self.get_ninja(),
         )
 
         if self.config.extra_modules_path is not None:
@@ -182,7 +223,7 @@ class Builder:
         cmd += [ "-D%s='%s'" % (k, v) for (k, v) in cmake_vars.items() if v is not None]
         cmd.append(self.opencvdir)
         execute(cmd)
-        execute(["ninja", "install/strip"])
+        execute([self.get_ninja(), "install/strip"])
 
     def build_javadoc(self):
         classpaths = []
@@ -251,6 +292,20 @@ if __name__ == "__main__":
     if not 'ANDROID_HOME' in os.environ and 'ANDROID_SDK' in os.environ:
         os.environ['ANDROID_HOME'] = os.environ["ANDROID_SDK"]
 
+    if not 'ANDROID_SDK' in os.environ:
+        raise Fail("SDK location not set. Either pass --sdk_path or set ANDROID_SDK environment variable")
+
+    # look for an NDK installed with the Android SDK
+    if not 'ANDROID_NDK' in os.environ and 'ANDROID_SDK' in os.environ and os.path.exists(os.path.join(os.environ["ANDROID_SDK"], 'ndk-bundle')):
+        os.environ['ANDROID_NDK'] = os.path.join(os.environ["ANDROID_SDK"], 'ndk-bundle')
+
+    if not 'ANDROID_NDK' in os.environ:
+        raise Fail("NDK location not set. Either pass --ndk_path or set ANDROID_NDK environment variable")
+
+    if not check_executable(['ccache', '--version']):
+        log.info("ccache not found - disabling ccache supprt")
+        args.no_ccache = True
+
     if os.path.realpath(args.work_dir) == os.path.realpath(SCRIPT_DIR):
         raise Fail("Specify workdir (building from script directory is not supported)")
     if os.path.realpath(args.work_dir) == os.path.realpath(args.opencv_dir):