CMake: Add back stricter warnings used in Serenity builds

These used to be enabled in `serenity_compile_options.cmake` for
Serenity builds and were removed in 9b05fb98. This is a slightly more
conservative subset of those, with ones that are enabled by default
omitted.

This should prevent our code quality regressing in the long run.

Meta/CMake/common_compile_options.cmake

@@ -19,8 +19,12 @@ else()
     add_compile_options(-ffp-contract=off)
 endif()
 
-add_compile_options(-Wno-invalid-offsetof)
+add_compile_options(-Wcast-qual)
+add_compile_options(-Wformat=2)
+add_compile_options(-Wimplicit-fallthrough)
+add_compile_options(-Wsuggest-override)
 
+add_compile_options(-Wno-invalid-offsetof)
 add_compile_options(-Wno-unknown-warning-option)
 add_compile_options(-Wno-unused-command-line-argument)
 

Userland/Libraries/LibGfx/ImageFormats/JPEGWriter.cpp

@@ -89,7 +89,7 @@ ErrorOr<void> JPEGWriter::encode_impl(Stream& stream, auto const& bitmap, Option
 
     while (cinfo.next_scanline < cinfo.image_height) {
         auto const* row_ptr = reinterpret_cast<u8 const*>(bitmap.scanline(cinfo.next_scanline));
-        JSAMPROW row_pointer = (JSAMPROW)row_ptr;
+        JSAMPROW row_pointer = const_cast<JSAMPROW>(row_ptr);
         jpeg_write_scanlines(&cinfo, &row_pointer, 1);
     }