GCC: enable -Wall and -Werror for all build types

Also make protobuf flags consistent across build types so that release builds
pass

Author: lethosor

CMakeLists.txt

@@ -244,9 +244,10 @@ if(UNIX)
     # enable C++11 features
     add_definitions(-DLINUX_BUILD)
     add_definitions(-D_GLIBCXX_USE_C99)
-    set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -g -Wall -Wno-unused-variable")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility=hidden -mtune=generic")
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fvisibility=hidden -mtune=generic")
+    set(GCC_COMMON_FLAGS "-fvisibility=hidden -mtune=generic -Wall -Werror -Wno-unused-variable")
+    set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -g")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GCC_COMMON_FLAGS}")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${GCC_COMMON_FLAGS}")
     if(DFHACK_BUILD_64)
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m64 -mno-avx")
         set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -m64 -mno-avx")

depends/protobuf/CMakeLists.txt

@@ -145,8 +145,8 @@ set(LIBPROTOC_SRCS
 list(APPEND LIBPROTOBUF_FULL_SRCS ${LIBPROTOBUF_LITE_SRCS})
 
 if(CMAKE_COMPILER_IS_GNUCC)
-    set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -Wno-sign-compare")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-result -Wno-unused-local-typedefs -Wno-misleading-indentation -Wno-class-memaccess")
+    set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-result -Wno-unused-local-typedefs -Wno-misleading-indentation -Wno-class-memaccess -Wno-sign-compare")
 elseif(MSVC)
     # Disable warnings for integer conversion to smaller type
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4267")