Only apply Apple cross-compile patches on macOS

Author: zanieb

cpython-unix/build-cpython.sh

@@ -70,12 +70,14 @@ cat Makefile.extra
 pushd Python-${PYTHON_VERSION}
 
 # configure doesn't support cross-compiling on Apple. Teach it.
-if [ "${PYTHON_MAJMIN_VERSION}" = "3.13" ]; then
-    patch -p1 -i ${ROOT}/patch-apple-cross-3.13.patch
-elif [ "${PYTHON_MAJMIN_VERSION}" = "3.12" ]; then
-    patch -p1 -i ${ROOT}/patch-apple-cross-3.12.patch
-else
-    patch -p1 -i ${ROOT}/patch-apple-cross.patch
+if [ "${PYBUILD_PLATFORM}" = "macos" ]; then
+    if [ "${PYTHON_MAJMIN_VERSION}" = "3.13" ]; then
+        patch -p1 -i ${ROOT}/patch-apple-cross-3.13.patch
+    elif [ "${PYTHON_MAJMIN_VERSION}" = "3.12" ]; then
+        patch -p1 -i ${ROOT}/patch-apple-cross-3.12.patch
+    else
+        patch -p1 -i ${ROOT}/patch-apple-cross.patch
+    fi
 fi
 
 # This patch is slightly different on Python 3.10+.