build: introduce variable DEPS_IGNORE_SHA for skipping dependency hash check

This will reduce friction as developers no longer need to provide a hash
when testing out different commits.

To skip the hash check, set `DEPS_IGNORE_SHA` to `TRUE` in
`cmake.deps/CMakeLists.txt`.

cmake/Deps.cmake

@@ -54,3 +54,11 @@ if(CMAKE_OSX_ARCHITECTURES)
     set(DEPS_C_COMPILER "${DEPS_C_COMPILER} -arch ${ARCH}")
   endforeach()
 endif()
+
+function(get_sha name ignore)
+  unset(EXTERNALPROJECT_URL_HASH)
+  if(NOT ${ignore})
+    string(TOUPPER ${name} name_allcaps)
+    set(EXTERNALPROJECT_URL_HASH URL_HASH SHA256=${${name_allcaps}_SHA256} PARENT_SCOPE)
+  endif()
+endfunction()