Add CMakeLists.txt wrapper

This is attempt to simplify using this repository few steps further. It
uses the CMake `FetchContent` module to download PHP sources, adds CMake
files and patches PHP sources.

Usage:

```sh
cmake -B php-build
cmake --build php-build -j
```

Author: petk

.gitignore

@@ -8,3 +8,8 @@
 
 # All PHP downloaded archives and extracted directories.
 /php-*
+
+# CMake-related files.
+/CMakeCache.txt
+/CMakeFiles/
+/CMakeUserPresets.json

CMakeLists.txt

@@ -0,0 +1,152 @@
+# Wrapper for integrating PHP sources with CMake
+#
+# This file uses the FetchContent module to download the PHP source code (from
+# a tarball), integrate additional CMake files, and apply necessary patches to
+# enable building PHP with CMake.
+#
+# While not part of the CMake-based build system itself, this file serves as a
+# wrapper to bridge the upstream PHP source code with the CMake-based build
+# system in this repository, streamlining the integration process.
+
+cmake_minimum_required(VERSION 3.25...3.31)
+
+if(CMAKE_SOURCE_DIR PATH_EQUAL CMAKE_BINARY_DIR)
+  message(
+    FATAL_ERROR
+    "In-source builds are disabled. Please, set the build directory.\n"
+    "For example:\n"
+    "  cmake -B php-build\n"
+    "  cmake --build php-build -j"
+  )
+endif()
+
+project(
+  PhpBuildSystem
+  VERSION 8.3
+  DESCRIPTION "CMake-based PHP build system"
+  HOMEPAGE_URL "https://github.com/petk/php-build-system"
+  LANGUAGES NONE
+)
+
+set(phpVersion "${PhpBuildSystem_VERSION}-dev")
+set(phpBranch "PHP-${PhpBuildSystem_VERSION}")
+set(phpSourceDir "${CMAKE_CURRENT_BINARY_DIR}/php-src")
+set(phpBinaryDir "${CMAKE_CURRENT_BINARY_DIR}/php")
+
+include(FetchContent)
+
+FetchContent_Declare(
+  php
+  URL https://github.com/php/php-src/archive/refs/heads/${phpBranch}.tar.gz
+  SOURCE_DIR ${phpSourceDir}
+  BINARY_DIR ${phpBinaryDir}
+  PATCH_COMMAND
+    ${CMAKE_COMMAND}
+    -P
+    ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/PhpBuildSystem/patch.cmake
+)
+
+# Create script for the FetchContent_Declare(PATCH_COMMAND).
+file(
+  CONFIGURE
+  OUTPUT CMakeFiles/PhpBuildSystem/patch.cmake
+  CONTENT [=[
+    message(STATUS "Adding CMake files to PHP sources")
+    file(COPY "@CMAKE_CURRENT_SOURCE_DIR@/cmake/" DESTINATION "@phpSourceDir@")
+
+    string(REGEX MATCH [[^([0-9]+\.[0-9]+)]] _ "@PhpBuildSystem_VERSION@")
+    file(
+      GLOB
+      patches
+      "@CMAKE_CURRENT_SOURCE_DIR@/patches/${CMAKE_MATCH_1}/*.patch"
+    )
+
+    if(NOT patches)
+      return()
+    endif()
+
+    find_package(Git QUIET)
+    if(NOT Git_FOUND)
+      # See: https://gitlab.kitware.com/cmake/cmake/-/merge_requests/10164
+      if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.32)
+        find_package(Patch QUIET)
+      else()
+        find_program(Patch_EXECUTABLE patch)
+        if(Patch_EXECUTABLE)
+          set(Patch_FOUND TRUE)
+        endif()
+      endif()
+    endif()
+
+    if(NOT Git_FOUND AND NOT Patch_FOUND)
+      message(WARNING "Patches not applied. Install Git or the patch command.")
+      return()
+    endif()
+
+    message(STATUS "Applying patches to PHP sources\n")
+
+    if(Git_FOUND)
+      # Add .git directory to be able to apply patches.
+      execute_process(
+        COMMAND ${GIT_EXECUTABLE} init
+        WORKING_DIRECTORY "@phpSourceDir@"
+        RESULT_VARIABLE result
+        OUTPUT_VARIABLE output
+        ERROR_VARIABLE error
+        ERROR_STRIP_TRAILING_WHITESPACE
+        OUTPUT_QUIET
+      )
+      if(NOT result EQUAL 0)
+        message(WARNING "Failed to create .git directory:\n${output}\n${error}")
+      endif()
+
+      execute_process(
+        COMMAND ${GIT_EXECUTABLE} apply --ignore-whitespace ${patches}
+        WORKING_DIRECTORY "@phpSourceDir@"
+        RESULT_VARIABLE result
+        OUTPUT_VARIABLE output
+        ERROR_VARIABLE error
+        ERROR_STRIP_TRAILING_WHITESPACE
+        OUTPUT_QUIET
+      )
+      if(NOT result EQUAL 0)
+        message(WARNING "Failed to apply patches:\n${output}\n${error}.")
+      endif()
+
+      # Clean temporary .git directory. Checks are done as safeguards.
+      if(
+        IS_DIRECTORY "@phpSourceDir@/.git"
+        AND EXISTS "@phpSourceDir@/main/php_version.h"
+        AND EXISTS "@phpSourceDir@/CMakeLists.txt"
+      )
+        file(REMOVE_RECURSE "@phpSourceDir@/.git/")
+      endif()
+    elseif(Patch_FOUND)
+      foreach(patch IN LISTS patches)
+        execute_process(
+          COMMAND ${Patch_EXECUTABLE} -p1 -i "${patch}"
+          WORKING_DIRECTORY "@phpSourceDir@"
+          RESULT_VARIABLE result
+          OUTPUT_VARIABLE output
+          ERROR_VARIABLE error
+          ERROR_STRIP_TRAILING_WHITESPACE
+          OUTPUT_QUIET
+        )
+        if(NOT result EQUAL 0)
+          cmake_path(GET patch FILENAME filename)
+          message(WARNING "Patch ${filename} failed:\n${output}\n${error}\n")
+        endif()
+      endforeach()
+    endif()
+  ]=]
+  @ONLY
+)
+
+cmake_path(
+  RELATIVE_PATH
+  phpSourceDir
+  BASE_DIRECTORY ${CMAKE_SOURCE_DIR}
+  OUTPUT_VARIABLE phpSourceDirRelative
+)
+message(STATUS "Downloading PHP ${phpVersion} to ${phpSourceDirRelative}")
+FetchContent_MakeAvailable(php)