[feature] Added cross-building conf variable

conan/tools/build/cross_building.py

@@ -9,6 +9,9 @@ def cross_building(conanfile=None, skip_x64_x86=False):
            x86_64 to x86, sparcv9 to sparc or ppc64 to ppc32
     :return: ``True`` if we are cross building, ``False`` otherwise.
     """
+    force = conanfile.conf.get("tools.build.cross_building:force", check_type=bool)
+    if force is not None:
+        return force
 
     build_os = conanfile.settings_build.get_safe('os')
     build_arch = conanfile.settings_build.get_safe('arch')

conans/model/conf.py

@@ -108,6 +108,7 @@
     "tools.apple:enable_visibility": "(boolean) Enable/Disable Visibility Apple Clang flags",
     "tools.env.virtualenv:powershell": "If it is set to True it will generate powershell launchers if os=Windows",
     # Compilers/Flags configurations
+    "tools.build.cross_building:force": "Force cross-building regardless of arch/OS settings.",
     "tools.build:compiler_executables": "Defines a Python dict-like with the compilers path to be used. Allowed keys {'c', 'cpp', 'cuda', 'objc', 'objcxx', 'rc', 'fortran', 'asm', 'hip', 'ispc'}",
     "tools.build:cxxflags": "List of extra CXX flags used by different toolchains like CMakeToolchain, AutotoolsToolchain and MesonToolchain",
     "tools.build:cflags": "List of extra C flags used by different toolchains like CMakeToolchain, AutotoolsToolchain and MesonToolchain",

conans/test/unittests/tools/build/test_cross_building.py

@@ -0,0 +1,16 @@
+import pytest
+
+from conan.tools.build import cross_building
+from conans.test.utils.mocks import ConanFileMock
+
+
+@pytest.mark.parametrize("force", (True, False))
+def test_using_force_conf(force):
+    """
+    Tests cross_building function is using the conf variable to force or not.
+
+    Issue related: https://github.com/conan-io/conan/issues/15392
+    """
+    conanfile = ConanFileMock()
+    conanfile.conf.define("tools.build.cross_building:force", force)
+    assert cross_building(conanfile) == force