android: Extract version from llvm-project instead of hardcoding it

Stop hardcoding LLVM version as 12, instead read it from external/llvm-project.

In 81e20472a0
the location of the LLVM_VERSION_MAJOR definition was moved. This patch accounts for that
by extracting the version from the new location if it exists. If the new file is not present,
it falls back to the old location.

Backport-to: 24.2
Tested-by: Antonio Ospite <antonio.ospite@collabora.com>
Tested-by: Alessandro Astone <alessandro.astone@canonical.com>
Reviewed-by: Mauro Rossi <issor.oruam@gmail.com>
Signed-off-by: Valentine Burley <valentine.burley@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30598>

android/Android.mk

@@ -27,6 +27,12 @@ LOCAL_PATH := $(call my-dir)
 MESA3D_TOP := $(dir $(LOCAL_PATH))
 
 LIBDRM_VERSION = $(shell cat external/libdrm/meson.build | grep -o "\<version\>\s*:\s*'\w*\.\w*\.\w*'" | grep -o "\w*\.\w*\.\w*" | head -1)
+LLVM_VERSION_MAJOR = $(shell \
+    if [ -f external/llvm-project/cmake/Modules/LLVMVersion.cmake ]; then \
+        grep 'set.LLVM_VERSION_MAJOR ' external/llvm-project/cmake/Modules/LLVMVersion.cmake | grep -o '[0-9]\+'; \
+    else \
+        grep 'set.LLVM_VERSION_MAJOR ' external/llvm-project/llvm/CMakeLists.txt | grep -o '[0-9]\+'; \
+    fi)
 
 MESA_VK_LIB_SUFFIX_amd := radeon
 MESA_VK_LIB_SUFFIX_intel := intel
@@ -86,8 +92,8 @@ MESON_GEN_PKGCONFIGS += DirectX-Headers
 endif
 
 ifneq ($(MESON_GEN_LLVM_STUB),)
-MESON_LLVM_VERSION := 12.0.0
-LOCAL_SHARED_LIBRARIES += libLLVM12
+MESON_LLVM_VERSION := $(LLVM_VERSION_MAJOR).0.0
+LOCAL_SHARED_LIBRARIES += libLLVM$(LLVM_VERSION_MAJOR)
 endif
 
 ifeq ($(shell test $(PLATFORM_SDK_VERSION) -ge 30; echo $$?), 0)