AGS: Fix Usage Of Undefined Preprocessor Define GCC Compiler Warning #2107

Job	Run time
Ubuntu (ubuntu-latest, sdl2-config, ccache g++, liba52-dev libcurl4-openssl-dev libfaad-dev libfl...	2m 34s
Xcode (macosx, -scheme ScummVM-macOS -destination 'platform=macOS,arch=x86_64', --disable-nasm --...	27m 49s
Ubuntu (ubuntu-20.04, sdl-config, ccache g++-4.8, g++-4.8 liba52-dev libcurl4-openssl-dev libfaad...	2m 58s
Windows (win32, x86-windows, x86, --enable-discord --enable-faad --enable-gif --enable-mikmod --e...	22m 54s
Xcode (ios7, -scheme ScummVM-iOS CODE_SIGN_IDENTITY="" CODE_SIGNING_ALLOWED=NO, --use-xcframework...	20m 20s
Windows (x64, x64, x64-windows, --enable-discord --enable-faad --enable-gif --enable-mikmod --ena...	22m 10s
Windows (arm64, arm64, arm64-windows, --enable-discord --enable-faad --enable-gif --enable-mikmod...	20m 56s
	1h 59m 41s

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