avoid precompiled-headers by default
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -853,7 +853,7 @@ add_library(rosegardenprivate ${RG_LIBRARY_TYPE}
 
 # If we've got cmake 3.16.0 or greater, use precompiled headers.
 # Cuts build time almost in half.
-if(NOT ${CMAKE_VERSION} VERSION_LESS "3.16.0")
+if(NOT ${CMAKE_VERSION} VERSION_LESS "3.16.0" AND NOT DISABLE_PCH)
   target_precompile_headers(rosegardenprivate
     PRIVATE
       # There's definitely a point where gcc slows down with too many