Missing make rules | Arch Linux

[UltraBlackLinux]

Hey there, I am currently trying to compile the 2013 source sdk, but I ran into a problem:

$ pwd
/home/maus/Documents/valve/source-sdk-2013/sp/src

$ ../../../steam-runtime/shell.sh --arch=i386
Setting up for build targeting i386

$ STEAM_RUNTIME_PATH=/home/maus/Documents/valve/steam-runtime make -f everything.mak
make[1]: Entering directory '/home/maus/Documents/valve/source-sdk-2013/sp/src'
Building: tier1
Building: mathlib
Building: raytrace
Building: vgui_controls
make[2]: Entering directory '/home/maus/Documents/valve/source-sdk-2013/sp/src/vgui2/vgui_controls'
make[2]: Entering directory '/home/maus/Documents/valve/source-sdk-2013/sp/src/raytrace'
make[2]: Entering directory '/home/maus/Documents/valve/source-sdk-2013/sp/src/mathlib'
make[2]: Entering directory '/home/maus/Documents/valve/source-sdk-2013/sp/src/tier1'
make[2]: *** No rule to make target '/home/maus/Documents/steam/source-sdk-2013/sp/src/raytrace/raytrace.cpp', needed by 'obj_raytrace_linux32/release/raytrace.o'.  Stop.
make[2]: Leaving directory '/home/maus/Documents/valve/source-sdk-2013/sp/src/raytrace'
make[1]: *** [everything.mak:52: raytrace] Error 2
make[1]: *** Waiting for unfinished jobs....
make[2]: *** No rule to make target '/home/maus/Documents/steam/source-sdk-2013/sp/src/mathlib/3dnow.cpp', needed by 'obj_mathlib_linux32/release/3dnow.o'.  Stop.
make[2]: Leaving directory '/home/maus/Documents/valve/source-sdk-2013/sp/src/mathlib'
make[1]: *** [everything.mak:48: mathlib] Error 2
make[2]: *** No rule to make target '/home/maus/Documents/steam/source-sdk-2013/sp/src/tier1/bitbuf.cpp', needed by 'obj_tier1_linux32/release/bitbuf.o'.  Stop.
make[2]: Leaving directory '/home/maus/Documents/valve/source-sdk-2013/sp/src/tier1'
make[1]: *** [everything.mak:68: tier1] Error 2
make[2]: *** No rule to make target '/home/maus/Documents/steam/source-sdk-2013/sp/src/vgui2/vgui_controls/../../public/filesystem_helpers.cpp', needed by 'obj_vgui_controls_linux32/release/filesystem_helpers.o'.  Stop.
make[2]: Leaving directory '/home/maus/Documents/valve/source-sdk-2013/sp/src/vgui2/vgui_controls'
make[1]: *** [everything.mak:72: vgui_controls] Error 2
make[1]: Leaving directory '/home/maus/Documents/valve/source-sdk-2013/sp/src'
make: *** [everything.mak:23: all] Error 2

OS Info:

$ inxi -Faz
System:    Kernel: 5.14.16-zen1-1-zen x86_64 bits: 64 compiler: gcc v: 11.1.0
           parameters: BOOT_IMAGE=/@/boot/vmlinuz-linux-zen root=UUID=2a555427-5d35-463f-8011-b023a855b928 rw
           rootflags=subvol=@ loglevel=3 quiet splash lsm=lockdown,yama,apparmor,bpf
           Desktop: KDE Plasma 5.23.2 tk: Qt 5.15.2 info: latte-dock wm: kwin_x11 vt: 2 dm: Ly Distro: Garuda Linux
           base: Arch Linux
....

Does anybody have an idea why this is happening? This is my 2nd attempt following this guide. Thanks!

[UltraBlackLinux]

switched to gmod