Add android ndk support to scons

SConstruct

@@ -103,6 +103,8 @@ opts.AddVariables(
     PathVariable('gtkdir', 'Directory where GTK SDK is installed.', "", OptionalPath),
     PathVariable('luadir', 'Directory where Lua binary package is unpacked.', "", OptionalPath),
     ('host', 'Cross-compile host.', ''),
+    PathVariable('ndkdir', 'Root directory of android NDK to use', "", OptionalPath),
+    ('android_api', 'Target android api', 31),
     EnumVariable('multilib_arch', 'Address model for multilib compiler: 32-bit or 64-bit', "", ["", "32", "64"]),
     ('jobs', 'Set the number of parallel compilations', "1", lambda key, value, env: int(value), int),
     BoolVariable('distcc', 'Use distcc', False),

scons/android-ndk.py

@@ -0,0 +1,34 @@
+# vi: syntax=python:et:ts=4
+import json
+
+#Intended usage:
+#- env["ndkdir"] set to ndk home
+#- env["android_api"] set to target api
+#- host needs to be set to android-$ABI where $ABI is one of keys in 
+#    ndkdir/meta/abis.json
+#- prefix needs to be set to sysroot containing cross-compiled 
+#    dependencies for matching android abi
+
+def exists(env):
+    return True
+
+def generate(env):
+    api = env["android_api"]
+    ndk = env["ndkdir"]
+
+    assert ndk
+
+    android, abi = env["host"].split("-", 1)
+    assert android == "android"
+
+    abi_spec = json.load(open(ndk + "/meta/abis.json"))[abi]
+    print(abi_spec)
+    env["ANDROID_TOOLCHAIN"] = f"{ndk}/toolchains/llvm/prebuilt/linux-x86_64"
+    env["AR"] = "$ANDROID_TOOLCHAIN/bin/llvm-ar"
+    env["CC"] = "$ANDROID_TOOLCHAIN/bin/clang"
+    env["CXX"] = "$ANDROID_TOOLCHAIN/bin/clang++"
+    #env["LINK"] = "$ANDROID_TOOLCHAIN/bin/ld"
+    env["RANLIB"] = "$ANDROID_TOOLCHAIN/bin/llvm-ranlib"
+    env["ANDROID_LLVM_TRIPLE"] = abi_spec["llvm_triple"]
+    env.Append(CCFLAGS = "-target $ANDROID_LLVM_TRIPLE$android_api")
+    env.Append(LINKFLAGS = "-target $ANDROID_LLVM_TRIPLE$android_api")

scons/cross_compile.py

@@ -11,16 +11,19 @@ def setup_cross_compile(env):
         env.Tool("default")
 
     if env["host"]:
-        tools = [
-            "CXX",
-            "CC",
-            "AR",
-            "RANLIB",
-            "RC"
+        if env["host"].startswith("android-"):
+            env.Tool("android-ndk")
+        else:
+            tools = [
+                "CXX",
+                "CC",
+                "AR",
+                "RANLIB",
+                "RC"
             ]
-        for tool in tools:
-            if tool in env:
-                env[tool] = env["host"] + "-" + env[tool]
+            for tool in tools:
+                if tool in env:
+                    env[tool] = env["host"] + "-" + env[tool]
 
         env.PrependUnique(CPPPATH="$prefix/include", LIBPATH="$prefix/lib")
         if not env["sdldir"] and env["PLATFORM"] == "win32":