Regression, building ros on ros RosBE2.1.6 'ninja bootcd -j1' does fail since some 0.4.15-dev commit at step237 during compiling boot/environ with random errors

Reproduction steps

• create VBox 4.3.12 VM with at least 2000MB of RAM spent to VM (you will need that much!)
• the virtual HDD should be at least 10GB (you will need that much)
• install ros into the VM, I used 0.4.15-dev-5188-gabafg0d1 GCC8.4.0 RosBEWin 2.2.1 here, I installed on FAT
• install git 2.10.0 from rapps
• install RosBE 2.1.6 from rapps, use C:\ros as the source folder
• switch desktop resolution to 1152x864 to have enough space for convenient working
• run RosBE2.1.6
• Run the taskmgr in the performance tab, and leave it running to observe resource consumption. Place it next to RosBE2.1.6 window
• now within the RosBE2.1.6 prompt do:
• 'prompt $T $P$G'
• 'git config --system http.sslverify false'
• 'git clone https://github.com/reactos/reactos.git'
• 'cd reactos' to enter the source tree. You should be in C:\ros\reactos now.
• 'git reset --hard 6ee2f98' to master 2019-02-25 23:00 (commit 0.4.12-dev-753-g6ee2f98) in your working-tree which is RosBE2.1.6compatible and builds successfully on Windows
• 'configure'
• 'cd output-MinGW-i386'
• 'ninja bootcd -j1'

Expected result
It should return to the prompt after successfully having created a bootcd, like it was still possible here. when I used 0.4.14-RC-38-g4111dfa as the guest, and tried to build the very same 0.4.12-dev-753-g6ee2f98 in the very same way. It succeeded back then
WinXPSP3 guest can ofc also successfully compile 0.4.12-dev-753-g6ee2f98 too ofc

Observed result
when performing this with 0.4.15-dev-5188-gabafg0d1that was built itself witth GCC8.4.0 RosBEWin 2.2.1 as a guest, it will fail with random errors during the build. See screenshot and logs
it failing to compile is very reproducible for me. I guess the poor Memory Management in master head is responsible for that, but that is just a guess
0.4.15-dev-5188-gabaf0d1_gcc840dbg_RosBEWin2_2_1_failed_to_build_that_bootcd.png
0.4.15-dev-5188-gabaf0d1_gcc840dbg_RosBEWin2_2_1_failed_to_build_that_bootcd.log