Fix "cpm_add_patches" handling of multiple patch commands

Update "cpm_add_patches" to correctly handle multiple patch
files. The "PATCH_COMMAND" executor may not be a shell, so
it is not portable to use shell operators like "&&" and "<"
in the command. Commands after the initial PATCH_COMMAND
should nstead be prefixed by COMMAND, and we can use "-i"
to specify that a file is used by the "patch" command.

Author: christopherbate

cmake/CPM.cmake

@@ -529,16 +529,16 @@ function(cpm_add_patches)
     # Convert to absolute path for use with patch file command.
     get_filename_component(PATCH_FILE "${PATCH_FILE}" ABSOLUTE)
 
-    # The first patch entry must be preceded by "PATCH_COMMAND" while the following items are
-    # preceded by "&&".
+    # The first patch entry must be preceded by "PATCH_COMMAND". Subsequent
+    # commands are preceeded by "COMMAND".
     if(first_item)
       set(first_item False)
       list(APPEND temp_list "PATCH_COMMAND")
     else()
-      list(APPEND temp_list "&&")
+      list(APPEND temp_list "COMMAND")
     endif()
     # Add the patch command to the list
-    list(APPEND temp_list "${PATCH_EXECUTABLE}" "-p1" "<" "${PATCH_FILE}")
+    list(APPEND temp_list "${PATCH_EXECUTABLE}" "-p1" "-i" "${PATCH_FILE}")
   endforeach()
 
   # Move temp out into parent scope.