Add tools.android:cmake_legacy_toolchain config

conan/tools/cmake/toolchain/blocks.py

@@ -261,6 +261,9 @@ class AndroidSystemBlock(Block):
         set(ANDROID_STL {{ android_stl }})
         {% endif %}
         set(ANDROID_ABI {{ android_abi }})
+        {% if android_define_legacy_toolchain_flag %}
+        set(ANDROID_USE_LEGACY_TOOLCHAIN_FILE {{ android_use_legacy_toolchain_file }})
+        {% endif %}
         include({{ android_ndk_path }}/build/cmake/android.toolchain.cmake)
         """)
 
@@ -278,11 +281,16 @@ def context(self):
             raise ConanException('CMakeToolchain needs tools.android:ndk_path configuration defined')
         android_ndk_path = android_ndk_path.replace("\\", "/")
 
+        use_cmake_legacy_toolchain = self._conanfile.conf.get("tools.android:cmake_legacy_toolchain")
+        legacy_toolchain_flag_defined = use_cmake_legacy_toolchain is not None
+
         ctxt_toolchain = {
             'android_platform': 'android-' + str(self._conanfile.settings.os.api_level),
             'android_abi': android_abi(self._conanfile),
             'android_stl': libcxx_str,
             'android_ndk_path': android_ndk_path,
+            'android_define_legacy_toolchain_flag': legacy_toolchain_flag_defined,
+            'android_use_legacy_toolchain_file': "ON" if use_cmake_legacy_toolchain else "OFF",
         }
         return ctxt_toolchain
 
@@ -564,6 +572,14 @@ def context(self):
         sharedlinkflags = self._conanfile.conf.get("tools.build:sharedlinkflags", default=[], check_type=list)
         exelinkflags = self._conanfile.conf.get("tools.build:exelinkflags", default=[], check_type=list)
         defines = self._conanfile.conf.get("tools.build:defines", default=[], check_type=list)
+
+        # See https://github.com/conan-io/conan/issues/13374
+        android_ndk_path = self._conanfile.conf.get("tools.android:ndk_path")
+        android_legacy_toolchain = self._conanfile.conf.get("tools.android:cmake_legacy_toolchain")
+        if android_ndk_path and (cxxflags or cflags) and android_legacy_toolchain is not False:
+            self._conanfile.output.warning("tools.build:cxxflags or cflags are defined, but Android NDK toolchain may be overriding "
+                                            "the values. Consider setting tools.android:cmake_legacy_toolchain to False.")
+
         return {
             "cxxflags": cxxflags,
             "cflags": cflags,

conans/model/conf.py

@@ -40,6 +40,7 @@
     "core.gzip:compresslevel": "The Gzip compresion level for Conan artifacts (default=9)",
     # Tools
     "tools.android:ndk_path": "Argument for the CMAKE_ANDROID_NDK",
+    "tools.android:cmake_legacy_toolchain": "Define to explicitly pass ANDROID_USE_LEGACY_TOOLCHAIN_FILE in CMake toolchain",
     "tools.build:skip_test": "Do not execute CMake.test() and Meson.test() when enabled",
     "tools.build:download_source": "Force download of sources for every package",
     "tools.build:jobs": "Default compile jobs number -jX Ninja, Make, /MP VS (default: max CPUs)",

conans/test/integration/toolchains/cmake/test_cmaketoolchain.py

@@ -579,6 +579,51 @@ def configure(self):
     assert "include(/foo/build/cmake/android.toolchain.cmake)" in conan_toolchain
     client.run("create . --name=foo --version=1.0 " + settings)
 
+@pytest.mark.parametrize("cmake_legacy_toolchain", [True, False, None])
+def test_android_legacy_toolchain_flag(cmake_legacy_toolchain):
+    client = TestClient()
+    conanfile = GenConanfile().with_settings("os", "arch")\
+        .with_generator("CMakeToolchain")
+    client.save({"conanfile.py": conanfile})
+    settings = "-s arch=x86_64 -s os=Android -s os.api_level=23 -c tools.android:ndk_path=/foo"
+    if cmake_legacy_toolchain is not None:
+        settings += f" -c tools.android:cmake_legacy_toolchain={cmake_legacy_toolchain}"
+        expected = "ON" if cmake_legacy_toolchain else "OFF"
+    client.run("install . " + settings)
+    conan_toolchain = client.load(os.path.join(client.current_folder, "conan_toolchain.cmake"))
+    if cmake_legacy_toolchain is not None:
+        assert f"set(ANDROID_USE_LEGACY_TOOLCHAIN_FILE {expected})" in conan_toolchain
+    else:
+        assert "ANDROID_USE_LEGACY_TOOLCHAIN_FILE" not in conan_toolchain
+
+
+@pytest.mark.parametrize("cmake_legacy_toolchain", [True, False, None])
+def test_android_legacy_toolchain_with_compileflags(cmake_legacy_toolchain):
+    # https://github.com/conan-io/conan/issues/13374
+    client = TestClient()
+    conanfile = GenConanfile().with_settings("os", "arch")\
+        .with_generator("CMakeToolchain")
+    profile = textwrap.dedent("""
+    [settings]
+    os=Android
+    os.api_level=23
+    arch=armv8
+
+    [conf]
+    tools.android:ndk_path=/foo
+    tools.build:cflags=["-foobar"]
+    tools.build:cxxflags=["-barfoo"]
+    """)
+    if cmake_legacy_toolchain is not None:
+        profile += f"\ntools.android:cmake_legacy_toolchain={cmake_legacy_toolchain}"
+
+    client.save({"conanfile.py": conanfile, "profile_host": profile})
+    client.run("install . -pr profile_host")
+    warning_text = "Consider setting tools.android:cmake_legacy_toolchain to False"
+    if cmake_legacy_toolchain is not False:
+        assert warning_text in client.out
+    else:
+        assert warning_text not in client.out
 
 @pytest.mark.skipif(platform.system() != "Windows", reason="Only Windows")
 def test_presets_paths_normalization():