cmake: support SKIP_DASHED_BUILT_INS

Just like the Makefile-based build learned to skip hard-linking the
dashed built-ins in 179227d (Optionally skip linking/copying the
built-ins, 2020-09-21), this patch teaches the CMake-based build the
same trick.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

contrib/buildsystems/CMakeLists.txt

@@ -685,13 +685,17 @@ endif()
 
 parse_makefile_for_executables(git_builtin_extra "BUILT_INS")
 
+option(SKIP_DASHED_BUILT_INS "Skip hardlinking the dashed versions of the built-ins")
+
 #Creating hardlinks
+if(NOT SKIP_DASHED_BUILT_INS)
 foreach(s ${git_SOURCES} ${git_builtin_extra})
 	string(REPLACE "${CMAKE_SOURCE_DIR}/builtin/" "" s ${s})
 	string(REPLACE ".c" "" s ${s})
 	file(APPEND ${CMAKE_BINARY_DIR}/CreateLinks.cmake "file(CREATE_LINK git${EXE_EXTENSION} git-${s}${EXE_EXTENSION})\n")
 	list(APPEND git_links ${CMAKE_BINARY_DIR}/git-${s}${EXE_EXTENSION})
 endforeach()
+endif()
 
 if(CURL_FOUND)
 	set(remote_exes