cmake: add knob to disable vcpkg

When building on windows users have the option to use vcpkg to provide
the dependencies needed to compile.  Previously, this was used only when
using the Visual Studio generator which was not ideal because:

  - Not all users who want to use vcpkg use the Visual Studio
    generators.

  - Some versions of Visual Studio 2019 moved away from using the
    VS 2019  generator by default, making it impossible for Visual
    Studio to configure the project in the likely event that it couldn't
    find the dependencies.

  - Inexperienced users of CMake are very likely to get tripped up by
    the errors caused by a lack of vcpkg, making the above bullet point
    both annoying and hard to debug.

As such, let's make using vcpkg the default on windows.  Users who want
to avoid using vcpkg can disable it by passing -DNO_VCPKG=TRUE.

Signed-off-by: Matthew Rogers <[email protected]>

Author: ROGERSM94

contrib/buildsystems/CMakeLists.txt

@@ -43,14 +43,23 @@ NOTE: By default CMake uses Makefile as the build tool on Linux and Visual Studi
 to use another tool say `ninja` add this to the command line when configuring.
 `-G Ninja`
 
+NOTE: By default CMake will install vcpkg locally to your source tree on configuration,
+to avoid this, add `-DNO_VCPKG=TRUE` to the command line when configuring.
+
 ]]
 cmake_minimum_required(VERSION 3.14)
 
 #set the source directory to root of git
 set(CMAKE_SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/../..)
-if(WIN32)
+
+option(USE_VCPKG "Whether or not to use vcpkg for obtaining dependencies.  Only applicable to Windows platforms" ON)
+if(NOT WIN32)
+	set(USE_VCPKG OFF CACHE BOOL FORCE)
+endif()
+
+if(USE_VCPKG)
 	set(VCPKG_DIR "${CMAKE_SOURCE_DIR}/compat/vcbuild/vcpkg")
-	if(MSVC AND NOT EXISTS ${VCPKG_DIR})
+	if(NOT EXISTS ${VCPKG_DIR})
 		message("Initializing vcpkg and building the Git's dependencies (this will take a while...)")
 		execute_process(COMMAND ${CMAKE_SOURCE_DIR}/compat/vcbuild/vcpkg_install.bat)
 	endif()
@@ -178,7 +187,9 @@ endif()
 
 find_program(MSGFMT_EXE msgfmt)
 if(NOT MSGFMT_EXE)
-	set(MSGFMT_EXE ${CMAKE_SOURCE_DIR}/compat/vcbuild/vcpkg/downloads/tools/msys2/msys64/usr/bin/msgfmt.exe)
+	if (USE_VCPKG)
+		set(MSGFMT_EXE ${CMAKE_SOURCE_DIR}/compat/vcbuild/vcpkg/downloads/tools/msys2/msys64/usr/bin/msgfmt.exe)
+	endif()
 	if(NOT EXISTS ${MSGFMT_EXE})
 		message(WARNING "Text Translations won't be built")
 		unset(MSGFMT_EXE)
@@ -982,7 +993,7 @@ file(APPEND ${CMAKE_BINARY_DIR}/GIT-BUILD-OPTIONS "NO_GETTEXT='${NO_GETTEXT}'\n"
 file(APPEND ${CMAKE_BINARY_DIR}/GIT-BUILD-OPTIONS "RUNTIME_PREFIX='${RUNTIME_PREFIX}'\n")
 file(APPEND ${CMAKE_BINARY_DIR}/GIT-BUILD-OPTIONS "NO_PYTHON='${NO_PYTHON}'\n")
 file(APPEND ${CMAKE_BINARY_DIR}/GIT-BUILD-OPTIONS "SUPPORTS_SIMPLE_IPC='${SUPPORTS_SIMPLE_IPC}'\n")
-if(WIN32)
+if(USE_VCPKG)
 	file(APPEND ${CMAKE_BINARY_DIR}/GIT-BUILD-OPTIONS "PATH=\"$PATH:$TEST_DIRECTORY/../compat/vcbuild/vcpkg/installed/x64-windows/bin\"\n")
 endif()