Read LLVM version from subdirectory

Rather than use a regex string search on the LLVM CMakeLists.txt, this
patch adds the LLVM project as a subdirectory and then reads the
version variables as properties. Additionally, this adds some new
variables to store packaging information, as including CPack resets
many of the variables used to configure CPack.

CMakeLists.txt

@@ -302,28 +302,6 @@ FetchContent_Declare(newlib
 FetchContent_MakeAvailable(llvmproject)
 FetchContent_MakeAvailable(${LLVM_TOOLCHAIN_C_LIBRARY})
 
-function(get_llvm_version_numbers llvmproject_SOURCE_DIR)
-    # Grab the version out of LLVM sources
-    file(
-        STRINGS ${llvmproject_SOURCE_DIR}/llvm/CMakeLists.txt version_strings
-        REGEX [[set\(LLVM_VERSION_[A-Z]+ [0-9]+\)]]
-    )
-    string(REGEX MATCH [[MAJOR ([0-9]+)]] unused "${version_strings}")
-    set(LLVM_VERSION_MAJOR ${CMAKE_MATCH_1} PARENT_SCOPE)
-    string(REGEX MATCH [[MINOR ([0-9]+)]] unused "${version_strings}")
-    set(LLVM_VERSION_MINOR ${CMAKE_MATCH_1} PARENT_SCOPE)
-    string(REGEX MATCH [[PATCH ([0-9]+)]] unused "${version_strings}")
-    set(LLVM_VERSION_PATCH ${CMAKE_MATCH_1} PARENT_SCOPE)
-endfunction()
-get_llvm_version_numbers(${llvmproject_SOURCE_DIR})
-
-project(
-    LLVMEmbeddedToolchainForArm
-    VERSION ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}
-    DESCRIPTION "LLVM Embedded Toolchain for Arm"
-    HOMEPAGE_URL "https://github.com/ARM-software/LLVM-embedded-toolchain-for-Arm"
-)
-
 # We generally want to install to a local directory to see what the
 # output will look like rather than install into the system, so change
 # the default accordingly.
@@ -346,7 +324,33 @@ if(LLVM_TOOLCHAIN_C_LIBRARY STREQUAL newlib)
     )
 endif()
 
-# These must be set before include(CPack) which the llvm CMakeLists.txt does.
+add_subdirectory(
+    ${llvmproject_SOURCE_DIR}/llvm llvm
+)
+
+get_directory_property(LLVM_VERSION_MAJOR DIRECTORY ${llvmproject_SOURCE_DIR}/llvm DEFINITION LLVM_VERSION_MAJOR)
+get_directory_property(LLVM_VERSION_MINOR DIRECTORY ${llvmproject_SOURCE_DIR}/llvm DEFINITION LLVM_VERSION_MINOR)
+get_directory_property(LLVM_VERSION_PATCH DIRECTORY ${llvmproject_SOURCE_DIR}/llvm DEFINITION LLVM_VERSION_PATCH)
+
+project(
+    LLVMEmbeddedToolchainForArm
+    VERSION ${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}
+    DESCRIPTION "LLVM Embedded Toolchain for Arm"
+    HOMEPAGE_URL "https://github.com/ARM-software/LLVM-embedded-toolchain-for-Arm"
+)
+
+# Set package name and version.
+if(DEFINED LLVM_TOOLCHAIN_PACKAGE_NAME)
+    set(PACKAGE_NAME ${LLVM_TOOLCHAIN_PACKAGE_NAME})
+else()
+    set(PACKAGE_NAME ${CMAKE_PROJECT_NAME})
+endif()
+set(CPACK_PACKAGE_NAME ${PACKAGE_NAME})
+set(PACKAGE_VERSION "${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")
+if(DEFINED LLVM_TOOLCHAIN_VERSION_SUFFIX)
+    set(PACKAGE_VERSION "${PACKAGE_VERSION}-${LLVM_TOOLCHAIN_VERSION_SUFFIX}")
+endif()
+
 # Restrict which LLVM components are installed.
 if(LLVM_TOOLCHAIN_NEWLIB_OVERLAY_INSTALL)
     set(CPACK_COMPONENTS_ALL
@@ -407,13 +411,14 @@ else()
     set(CPACK_SYSTEM_NAME "${CMAKE_SYSTEM_NAME}-${processor_name}")
 endif()
 
-add_subdirectory(
-    ${llvmproject_SOURCE_DIR}/llvm llvm
-)
+set(CPACK_PACKAGE_VERSION ${PACKAGE_VERSION})
 
 if(LLVM_TOOLCHAIN_NEWLIB_OVERLAY_INSTALL)
-    set(CPACK_PACKAGE_FILE_NAME ${CMAKE_PROJECT_NAME}-newlib-overlay-${CMAKE_PROJECT_VERSION})
+    set(PACKAGE_FILE_NAME ${PACKAGE_NAME}-newlib-overlay-${PACKAGE_VERSION})
+else()
+    set(PACKAGE_FILE_NAME ${PACKAGE_NAME}-${PACKAGE_VERSION}-${CPACK_SYSTEM_NAME})
 endif()
+set(CPACK_PACKAGE_FILE_NAME ${PACKAGE_FILE_NAME})
 
 # Including CPack again after llvm CMakeLists.txt included it
 # resets CPACK_PACKAGE_VERSION to the default MAJOR.MINOR.PATCH format.
@@ -2034,10 +2039,8 @@ else()
     set(cpack_generator TXZ)
     set(package_filename_extension ".tar.xz")
 endif()
-# CPACK_PACKAGE_FILE_NAME may refer to the source package so use this variable instead.
-set(binary_package_name ${CPACK_PACKAGE_NAME}-${CPACK_PACKAGE_VERSION}-${CPACK_SYSTEM_NAME})
-set(package_filepath ${CMAKE_BINARY_DIR}/${binary_package_name}${package_filename_extension})
-set(unpack_directory ${CMAKE_CURRENT_BINARY_DIR}/unpack/${binary_package_name})
+set(package_filepath ${CMAKE_BINARY_DIR}/${PACKAGE_FILE_NAME}${package_filename_extension})
+set(unpack_directory ${CMAKE_CURRENT_BINARY_DIR}/unpack/${PACKAGE_FILE_NAME})
 add_custom_command(
     OUTPUT ${package_filepath}
     COMMAND "${CMAKE_COMMAND}" -E rm -f ${package_filepath}