Compilation fails if gold does not exist

[themancalledjakob]

The gold linker is being deprecated, and its non-existence has already arrived on some distros.
We're adding -fuse-ld=gold though to our common linux64 makefile. This quite unnecessarily breaks compilation.

The fix may be confusing for the uninformed (who isn't), as the error message mentions neither gold nor the responsible Makefile (libs/openFrameworksCompiled/project/linux64/config.linux64.default.mk).

The error message:

[...]
g++ -o bin/glInfoExample  obj/linux64/Release/src/glewOutput.o obj/linux64/Release/src/main.o obj/linux64/Release/src/ofApp.o   ../../../libs/openFrameworksCompiled/lib/linux64/libopenFrameworks.a  -Wl,-rpath=./libs:./bin/libs:./ -Wl,--as-needed -Wl,--gc-sections -fuse-ld=gold -L../../../libs/fmod/lib/linux64/ -lfmod ../../../libs/kiss/lib/linux64/libkiss.a ../../../libs/tess2/lib/linux64/libtess2.a -lz -lgstapp-1.0 -lgstvideo-1.0 -lgstbase-1.0 -lgstreamer-1.0 -ludev -lfontconfig -lfreetype -lsndfile -lopenal -lssl -lcrypto -lcurl -lglfw -lrtaudio -lpulse-simple -pthread -lpulse -pthread -lasound -lGL -lGLEW -lGL -lX11 -lGLU -lOpenGL -lgtk-3 -lgdk-3 -lz -lpangocairo-1.0 -lpango-1.0 -lharfbuzz -latk-1.0 -lcairo-gobject -lcairo -lgdk_pixbuf-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lmpg123 -lglut -lX11 -lXrandr -lXxf86vm -lXi -lXcursor -ldl -lpthread -lfreeimage -lpugixml -luriparser -lXinerama
collect2: fatal error: cannot find 'ld'
compilation terminated.
make[1]: *** [../../../libs/openFrameworksCompiled/project/makefileCommon/compile.project.mk:411: bin/glInfoExample] Error 1
make[1]: Leaving directory '/home/jrkb/openFrameworks2025/examples/gl/glInfoExample'
make: *** [../../../libs/openFrameworksCompiled/project/makefileCommon/compile.project.mk:131: Release] Error 2

I therefore propose to fix it before gold is nowhere to be found.

We can even conditionally use either mold, gold, or ld.

See PR #8468

[themancalledjakob]

Oh, I now see there is already #8255, which includes a very similar fix.