This bug report is actually meant for the 4.20 branch but I couldn’t select it in the dropdown list.
Building on Arch Linux with clang 6.0.0 fails almost immediately:
------- Build details --------
Using system toolchain.
Using clang (/usr/bin/clang++) version '6.0.0' (string), 6 (major), 0 (minor), 0 (patch)
Using bundled libc++ standard C++ library.
Using lld linker
Using ar and ranlib: /usr/bin/ar, /usr/bin/ranlib
Using fast way to relink circularly dependent libraries (no FixDeps).
Compiler is set up to generate position independent executables by default, but we're suppressing it.
------------------------------
Performing 20 actions (4 in parallel)
[3/20] Compile Module.Core.2_of_9.cpp
[1/20] Compile Module.Core.4_of_9.cpp
[2/20] Compile Module.Core.3_of_9.cpp
[4/20] Compile Module.Core.1_of_9.cpp
[5/20] Link (ld) libUnrealHeaderTool-BuildSettings.so
clang-6.0: warning: argument unused during compilation: '-nopie' [-Wunused-command-line-argument]
/usr/bin/ld: /home/dominator/UnrealEngine/Engine/Intermediate/Build/Linux/B4D820EA/UnrealHeaderTool/Development/BuildSettings/Module.BuildSettings.cpp.o: relocation R_X86_64_32 against `.rodata.str4.4' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Nonrepresentable section on output
clang-6.0: error: linker command failed with exit code 1 (use -v to see invocation)
It looks like the -nopie argument doesn’t take effect so maybe that’s the reason for the build failing?