dev-lang/mono-5.12.0.226 fails to build

[g0dsCookie]

After unmasking mono-5.12 and running emerge -1vu mono the build fails.

Relevant files:

• build.log
• emerge --info

It's complaining about some files missing even though they actually exist:

$ sudo ls -l /var/tmp/portage/dev-lang/mono-5.12.0.226/work/mono-5.12.0.226-abi_x86_64.amd64/mcs/build/common/basic-profile-check.cs
-rw-r--r-- 1 portage portage 1226 May  4 09:45 /var/tmp/portage/dev-lang/mono-5.12.0.226/work/mono-5.12.0.226-abi_x86_64.amd64/mcs/build/common/basic-profile-check.cs

and:

$ sudo ls -l /var/tmp/portage/dev-lang/mono-5.12.0.226/work/mono-5.12.0.226-abi_x86_64.amd64/mcs/class/Facades/System.Runtime/{TypeForwarders,AssemblyInfo}.cs
-rw-r--r-- 1 portage portage  1692 May  4 09:45 /var/tmp/portage/dev-lang/mono-5.12.0.226/work/mono-5.12.0.226-abi_x86_64.amd64/mcs/class/Facades/System.Runtime/AssemblyInfo.cs
-rw-r--r-- 1 portage portage 31177 May  4 09:45 /var/tmp/portage/dev-lang/mono-5.12.0.226/work/mono-5.12.0.226-abi_x86_64.amd64/mcs/class/Facades/System.Runtime/TypeForwarders.cs

mono-5.11 installs fine.

[dallenwilson]

Same problem, same files with mono-5.14.0.177.

Edit: I'm assuming it's a problem with my system, not the ebuild. I have another machine with 5.14.0.177 installed and didn't have any issues with it.