CMake: Remove hardcoded warnings list and forcing -Werror on library builds

The CMake buildsystem should be completely reviewed to properly match
what is done by SCons, instead of making its own arbitrary decisions on
how godot-cpp should be compiled.

Currently the SCons setup doesn't include warning options, so CMake
shouldn't either. Options similar to upstream Godot's SCons setup could
be added, and then replicated for CMake.

CMakeLists.txt

@@ -47,11 +47,6 @@ option(GODOT_CPP_WARNING_AS_ERROR "Treat warnings as errors" OFF)
 # Add path to modules
 list( APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/" )
 
-# Check if we are building ourself or being included
-if(${PROJECT_NAME} STREQUAL ${CMAKE_PROJECT_NAME})
-    set(GODOT_CPP_BUILDING_SELF ON)
-endif()
-
 # Set some helper variables for readability
 set( compiler_is_clang "$<OR:$<CXX_COMPILER_ID:AppleClang>,$<CXX_COMPILER_ID:Clang>>" )
 set( compiler_is_gnu "$<CXX_COMPILER_ID:GNU>" )
@@ -158,12 +153,6 @@ add_library(godot::cpp ALIAS ${PROJECT_NAME})
 
 include(GodotCompilerWarnings)
 
-# Treat warnings as errors if we are building ourself
-if(GODOT_CPP_BUILDING_SELF)
-    unset( GODOT_CPP_WARNING_AS_ERROR CACHE )
-    set_warning_as_error()
-endif()
-
 target_compile_features(${PROJECT_NAME}
 	PRIVATE
 		cxx_std_17

test/CMakeLists.txt

@@ -59,31 +59,9 @@ if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
 
 else()
 
-#elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-	# using Clang
-#elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-	# using GCC and maybe MinGW?
-
 	set(GODOT_LINKER_FLAGS "-static-libgcc -static-libstdc++ -Wl,-R,'$$ORIGIN'")
 
-	# Hmm.. maybe to strikt?
 	set(GODOT_COMPILE_FLAGS "-fPIC -g -Wwrite-strings")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wchar-subscripts -Wcomment -Wdisabled-optimization")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wformat -Wformat=2 -Wformat-security -Wformat-y2k")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wimport -Winit-self -Winline -Winvalid-pch -Werror")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wmissing-braces -Wmissing-format-attribute")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wmissing-include-dirs -Wmissing-noreturn -Wpacked -Wpointer-arith")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wredundant-decls -Wreturn-type -Wsequence-point")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wswitch -Wswitch-enum -Wtrigraphs")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wuninitialized -Wunknown-pragmas -Wunreachable-code -Wunused-label")
-	set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wunused-value -Wvariadic-macros -Wvolatile-register-var -Wno-error=attributes")
-
-	# -Wshadow -Wextra -Wall -Weffc++ -Wfloat-equal -Wstack-protector -Wunused-parameter -Wsign-compare -Wunused-variable -Wcast-align
-	# -Wunused-function -Wstrict-aliasing -Wstrict-aliasing=2 -Wmissing-field-initializers
-
-	if(NOT CMAKE_SYSTEM_NAME STREQUAL "Android")
-		set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -Wno-ignored-attributes")
-	endif()
 
 	if(CMAKE_BUILD_TYPE MATCHES Debug)
 		set(GODOT_COMPILE_FLAGS "${GODOT_COMPILE_FLAGS} -fno-omit-frame-pointer -O0")