Newbie: Getting Ovmf built

[Peter Wiehe <peter.wiehe2@gmail.com>]

Hello, I'm a total newbie to Tianocore/EDK2/OVMF.
(My coding is at high school level I think, not university level. I
have some (small) experience writing in Assembler, C, C++. I wrote a
little bootloader, so I know something about filesystem in general and
ext2 and pre-kernel "environment".)

I use xubuntu 18.04 on an AMD 64bit PC.

I'm currently trying to
1.) build OVMF from source
2.) and then want to run it in/with Qemu.
3.) Later I would like to try to write a simple ext2 "driver". Can't
guarantee I will succeed, but let's see.

So far I have
1.) downloaded the whole edk2 zip/tar-ball
2.) have installed nasm and ASL (iasl)
3.) Run "EmulatorPkg/build.sh"
4.) Run "OvmfPkg/build.sh -a X64"
5.) Run "OvmfPkg/build.sh -a X64 qemu"

Then I get the error message "qemu-system-x86_64: -pflash
/home/peter/Schreibtisch/edk2-master/Build/OvmfX64/DEBUG_GCC5/QEMU/bios.bin:
Could not open '/home/peter/Schreibtisch/edk2-master/Build/OvmfX64/DEBUG_GCC5/QEMU/bios.bin':
No such file or directory"

So my first question is how to deal with this error.

Kind regards
Peter Wiehe