Optionally install ICU if not available on the system

Author: triplef

README.md

@@ -18,7 +18,7 @@ The toolchain currently consists of the following libraries:
 - [libiconv](https://github.com/kiyolee/libiconv-win-build)
 - [libxml2](https://github.com/GNOME/libxml2)
 - [libxslt](https://github.com/GNOME/libxslt)
-- [ICU](https://docs.microsoft.com/en-us/windows/win32/intl/international-components-for-unicode--icu-) (DLL provided by Windows 10 version 1903 or later)
+- [ICU](https://docs.microsoft.com/en-us/windows/win32/intl/international-components-for-unicode--icu-) (using system-provided DLL on Windows 10 version 1903 or later)
 
 Prerequisites for Building
 --------------------------

patches/libxml2-windows-icu.patch renamed to patches/opt-libxml2-windows-icu.patch

@@ -0,0 +1,64 @@
+@echo off
+setlocal
+
+call "%~dp0\..\scripts\common.bat" loadenv || exit /b 1
+
+:: determine whether we can use the Windows-provided ICU
+:: (requires Windows 10 version 1903 / build 18362 or later)
+for /f "tokens=4-6 delims=. " %%i in ('ver') do (
+  set WIN_VERSION=%%i
+  set WIN_BUILD=%%k
+)
+if %WIN_VERSION% GTR 10 (
+  :: Windows 11 or later
+  set SKIP_ICU=1
+) else if %WIN_VERSION% EQU 10 (
+  if %WIN_BUILD% GEQ 18362 (
+    :: Windows 10 version 1903 / build 18362 or later
+    set SKIP_ICU=1
+  )
+)
+if defined SKIP_ICU (
+  echo Using system-provided ICU DLL ^(requires Windows 10 version 1903 or later^)
+  exit /b 0
+)
+
+if "%ARCH%" == "x86" (
+  set ICU_RELEASE_URL=https://github.com/unicode-org/icu/releases/download/release-69-1/icu4c-69_1-Win32-MSVC2019.zip
+) else if "%ARCH%" == "x64" (
+  set ICU_RELEASE_URL=https://github.com/unicode-org/icu/releases/download/release-69-1/icu4c-69_1-Win64-MSVC2019.zip
+) else (
+  echo Unknown ARCH: %ARCH%
+  exit /b 1
+)
+
+for %%a in ("%ICU_RELEASE_URL%") do (
+   set ICU_RELEASE_FILE=%%~nxa
+   set ICU_RELEASE_NAME=%%~na
+)
+
+if not exist "%CACHE_ROOT%" (mkdir "%CACHE_ROOT%" || exit /b 1)
+cd "%CACHE_ROOT%" || exit /b 1
+
+if not exist %ICU_RELEASE_FILE% (
+  echo.
+  echo ### Downloading release
+  curl -L -O# %ICU_RELEASE_URL% || exit /b 1
+)
+
+if not exist %ICU_RELEASE_NAME% (
+  echo.
+  echo ### Extracting release
+  powershell Expand-Archive %ICU_RELEASE_FILE% || exit /b 1
+)
+
+echo.
+echo ### Installing
+cd %ICU_RELEASE_NAME% || exit /b 1
+pushd bin* || exit /b 1
+xcopy /Y /F "icu*.dll" "%INSTALL_PREFIX%\lib\" || exit /b 1
+popd
+pushd lib* || exit /b 1
+xcopy /Y /F "icu*.lib" "%INSTALL_PREFIX%\lib\" || exit /b 1
+popd
+xcopy /Y /F /S "include\*" "%INSTALL_PREFIX%\include\" || exit /b 1

phases/15-icu.bat

@@ -13,7 +13,14 @@ for /f "usebackq delims=" %%i in (`call %BASH% '../scripts/get-latest-github-rel
 :: load environment and prepare project
 call "%~dp0\..\scripts\common.bat" prepare_project || exit /b 1
 
-cd "%SRCROOT%\%PROJECT%\win32" || exit /b 1
+cd "%SRCROOT%\%PROJECT%" || exit \b 1
+
+:: apply patch to use system-provided ICU DLL if applicable
+if not exist "%INSTALL_PREFIX%\lib\icu*.dll" (
+  git apply "%ROOT_DIR%\patches\opt-libxml2-windows-icu.patch" || exit /b 1
+)
+
+cd "win32" || exit /b 1
 
 echo.
 echo ### Running configure