gh-111225: Link extension modules against libpython on Android (#115780)

Part of the work on PEP 738: Adding Android as a supported platform.

* Rename the LIBPYTHON variable to MODULE_LDFLAGS, to more accurately 
  reflect its purpose.
* Edit makesetup to use MODULE_LDFLAGS when linking extension modules.
* Edit the Makefile so that extension modules depend on libpython on 
  Android and Cygwin.
* Restore `-fPIC` on Android. It was removed several years ago with a 
  note that the toolchain used it automatically, but this is no longer
  the case. Omitting it causes all linker commands to fail with an error
  like `relocation R_AARCH64_ADR_PREL_PG_HI21 cannot be used against
  symbol '_Py_FalseStruct'; recompile with -fPIC`.

configure.ac

@@ -1360,6 +1360,7 @@ if test $enable_shared = "yes"; then
   case $ac_sys_system in
     CYGWIN*)
       LDLIBRARY='libpython$(LDVERSION).dll.a'
+      BLDLIBRARY='-L. -lpython$(LDVERSION)'
       DLLLIBRARY='libpython$(LDVERSION).dll'
       ;;
     SunOS*)
@@ -3333,7 +3334,6 @@ then
 		 then CCSHARED="-fPIC";
 		 else CCSHARED="+z";
 		 fi;;
-	Linux-android*) ;;
 	Linux*|GNU*) CCSHARED="-fPIC";;
 	Emscripten*|WASI*)
 		AS_VAR_IF([enable_wasm_dynamic_linking], [yes], [
@@ -5888,11 +5888,13 @@ LDVERSION='$(VERSION)$(ABIFLAGS)'
 AC_MSG_RESULT([$LDVERSION])
 
 # On Android and Cygwin the shared libraries must be linked with libpython.
-AC_SUBST([LIBPYTHON])
+AC_SUBST([MODULE_DEPS_SHARED])
+AC_SUBST([MODULE_LDFLAGS])
+MODULE_DEPS_SHARED='$(MODULE_DEPS_STATIC) $(EXPORTSYMS)'
+MODULE_LDFLAGS=''
 if test "$PY_ENABLE_SHARED" = "1" && ( test -n "$ANDROID_API_LEVEL" || test "$MACHDEP" = "cygwin"); then
-  LIBPYTHON="-lpython${VERSION}${ABIFLAGS}"
-else
-  LIBPYTHON=''
+  MODULE_DEPS_SHARED="$MODULE_DEPS_SHARED \$(LDLIBRARY)"
+  MODULE_LDFLAGS="\$(BLDLIBRARY)"
 fi