Summary

GHC 8.6.5 and 8.8.3 (as well as master, I suspect) fails to build with LLD 10 as linker with following error:

HC [stage 1] utils/iserv/stage2_p/build/Main.p_o

cc: warning: argument unused during compilation: '-pthread' [-Wunused-command-line-argument]
ld: error: -r and --export-dynamic may not be used together
cc: error: linker command failed with exit code 1 (use -v to see invocation)
`cc' failed in phase `Linker'. (Exit code: 1)

The following patch is proposed for the fix:

--- utils/iserv/ghc.mk.orig     2020-03-23 22:25:01 UTC
+++ utils/iserv/ghc.mk
@@ -31,7 +31,7 @@ endif
 # of overhead to startup and increases the binary sizes) but if you
 # need it there's no alternative.
 ifeq "$(TargetElf)" "YES"
-ifneq "$(TargetOS_CPP)" "solaris2"
+ifeq "$(findstring $(TargetOS_CPP), solaris2 freebsd)" ""
 # The Solaris linker does not support --export-dynamic option. It also
 # does not need it since it exports all dynamic symbols by default
 utils/iserv_stage2_MORE_HC_OPTS += -optl-Wl,--export-dynamic

But I'm not sure if it is a proper fix, or a workaround.

Steps to reproduce

Get a recent FreeBSD 13-CURRENT and just run make -C /usr/ports/lang/ghc.