Meta: Disable the use of PCH by default

While this has a rather significant impact for me, it appears to have
very minimal build time improvements (or in some cases, regressions).
Also appears to cause some issues when building on macOS.
So disable it by default, but leave the option so people that get
something out of it (seems to mostly be a case of "is reading the
headers fast enough") can turn it on for their builds.

CMakeLists.txt

@@ -26,7 +26,7 @@ option(ENABLE_ALL_THE_DEBUG_MACROS "Enable all debug macros to validate they sti
 option(ENABLE_COMPILETIME_FORMAT_CHECK "Enable compiletime format string checks" ON)
 option(ENABLE_PCI_IDS_DOWNLOAD "Enable download of the pci.ids database at build time" ON)
 option(BUILD_LAGOM "Build parts of the system targeting the host OS for fuzzing/testing" OFF)
-option(PRECOMPILE_COMMON_HEADERS "Precompile some common headers to speedup compilation" ON)
+option(PRECOMPILE_COMMON_HEADERS "Precompile some common headers to speedup compilation" OFF)
 
 add_custom_target(run
     COMMAND ${CMAKE_SOURCE_DIR}/Meta/run.sh