Build: Add a flag to disable PCH

src/libslic3r/CMakeLists.txt

@@ -171,7 +171,7 @@ add_library(libslic3r STATIC
     SLA/SLASpatIndex.hpp
 )
 
-if (NOT SLIC3R_SYNTAXONLY)
+if (SLIC3R_PCH AND NOT SLIC3R_SYNTAXONLY)
     add_precompiled_header(libslic3r pchheader.hpp FORCEINCLUDE)
 endif ()
 

src/slic3r/CMakeLists.txt

@@ -128,6 +128,6 @@ add_library(libslic3r_gui STATIC
 )
 
 target_link_libraries(libslic3r_gui libslic3r avrdude imgui)
-if (NOT SLIC3R_SYNTAXONLY)
+if (SLIC3R_PCH AND NOT SLIC3R_SYNTAXONLY)
     add_precompiled_header(libslic3r_gui pchheader.hpp FORCEINCLUDE)
 endif ()