[PATCH 4/6] cmake: only look for "sh" in "C:/Program Files" on Windows

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Guard the finding of "SH_EXE" in "C:\Program Files" with a check for
whether we're on Windows.

This Windows-specific code was first added in [1], and later expanded
on [2], but since some of that was added this build recipe has been
made portable outside of Windows.

1. 72b6eeb81b1 (cmake: do find Git for Windows' shell interpreter,
   2020-09-28)
2. 476e54b1c60 (cmake: support local installations of git,
   2022-07-27).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 contrib/buildsystems/CMakeLists.txt | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index d45b9c8e00a..560a15ed35a 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -107,10 +107,17 @@ if(USE_VCPKG)
 	set(CMAKE_TOOLCHAIN_FILE ${VCPKG_DIR}/scripts/buildsystems/vcpkg.cmake CACHE STRING "Vcpkg toolchain file")
 endif()
 
-find_program(SH_EXE sh PATHS "C:/Program Files/Git/bin" "$ENV{LOCALAPPDATA}/Programs/Git/bin")
-if(NOT SH_EXE)
-	message(FATAL_ERROR "sh: shell interpreter was not found in your path, please install one."
-			"On Windows, you can get it as part of 'Git for Windows' install at https://gitforwindows.org/")
+if(WIN32)
+	find_program(SH_EXE sh PATHS "C:/Program Files/Git/bin" "$ENV{LOCALAPPDATA}/Programs/Git/bin")
+	if(NOT SH_EXE)
+		message(FATAL_ERROR "sh: shell interpreter was not found in your path, please install one."
+				"You can get it as part of 'Git for Windows' install at https://gitforwindows.org/")
+	endif()
+else()
+	find_program(SH_EXE sh)
+	if(NOT SH_EXE)
+		message(FATAL_ERROR "cannot find 'sh' in '$PATH'")
+	endif()
 endif()
 
 #Create GIT-VERSION-FILE using GIT-VERSION-GEN
-- 
2.39.0.1071.g97ce8966538