pkgsStatic.libunwind fails to build

[LBensman]

Describe the bug

Definition for pkgsStatic.libunwind fails to build.

To Reproduce

Steps to reproduce the behavior:

1. Execute nix-build -E '(import <nixpkgs>{}).pkgsStatic.libunwind'

Build fails with:

copying selected object files to avoid basename conflicts...
libtool: link: ln x86_64/longjmp.o .libs/libunwind-setjmp.lax/lt1-longjmp.o || cp x86_64/longjmp.o .libs/libunwind-setjmp.lax/lt1-longjmp.o
libtool: link: ln x86_64/siglongjmp.o .libs/libunwind-setjmp.lax/lt2-siglongjmp.o || cp x86_64/siglongjmp.o .libs/libunwind-setjmp.lax/lt2-siglongjmp.o
libtool: link: x86_64-unknown-linux-musl-ar cru .libs/libunwind-setjmp.a setjmp/longjmp.o setjmp/siglongjmp.o .libs/libunwind-setjmp.lax/lt1-longjmp.o .libs/libunwind-setjmp.lax/lt2-siglongjmp.o .libs/libunwind-setjmp.lax/libunwind-elf64.a/elf64.o
x86_64-unknown-linux-musl-ar: `u' modifier ignored since `D' is the default (see `U')
libtool: link: x86_64-unknown-linux-musl-ranlib .libs/libunwind-setjmp.a
libtool: link: rm -fr .libs/libunwind-setjmp.lax .libs/libunwind-setjmp.lax
libtool: link: ( cd ".libs" && rm -f "libunwind-setjmp.la" && ln -s "../libunwind-setjmp.la" "libunwind-setjmp.la" )
make[2]: Leaving directory '/tmp/nix-build-libunwind-1.3.1-x86_64-unknown-linux-musl.drv-0/libunwind-1.3.1/src'
make[1]: Leaving directory '/tmp/nix-build-libunwind-1.3.1-x86_64-unknown-linux-musl.drv-0/libunwind-1.3.1/src'
Making all in tests
make[1]: Entering directory '/tmp/nix-build-libunwind-1.3.1-x86_64-unknown-linux-musl.drv-0/libunwind-1.3.1/tests'
x86_64-unknown-linux-musl-gcc -DHAVE_CONFIG_H -I. -I../include  -I../include -D_GNU_SOURCE -DNDEBUG  -g -O2 -fexceptions -Wall -Wsign-compare -c -o forker.o forker.c
/nix/store/828g2nqfgivscv79xykkmgjk0znll08l-bash-4.4-p23/bin/bash ../libtool  --tag=CC   --mode=link x86_64-unknown-linux-musl-gcc  -g -O2 -fexceptions -Wall -Wsign-compare -static  -o forker forker.o
libtool: link: x86_64-unknown-linux-musl-gcc -g -O2 -fexceptions -Wall -Wsign-compare -o forker forker.o
x86_64-unknown-linux-musl-gcc -DHAVE_CONFIG_H -I. -I../include  -I../include -D_GNU_SOURCE -DNDEBUG  -g -O2 -fexceptions -Wall -Wsign-compare -c -o Gperf-simple.o Gperf-simple.c
/nix/store/828g2nqfgivscv79xykkmgjk0znll08l-bash-4.4-p23/bin/bash ../libtool  --tag=CC   --mode=link x86_64-unknown-linux-musl-gcc  -g -O2 -fexceptions -Wall -Wsign-compare   -o Gperf-simple Gperf-simple.o ../src/libunwind-x86_64.la ../src/libunwind.la
libtool: link: x86_64-unknown-linux-musl-gcc -g -O2 -fexceptions -Wall -Wsign-compare -o Gperf-simple Gperf-simple.o  ../src/.libs/libunwind-x86_64.a /tmp/nix-build-libunwind-1.3.1-x86_64-unknown-linux-musl.drv-0/libunwind-1.3.1/src/.libs/libunwind.a ../src/.libs/libunwind.a -lc -lgcc_s -llzma
/nix/store/9wfys2786kmc1z4dqy0a6g151s4q9vb6-x86_64-unknown-linux-musl-binutils-2.31.1/bin/x86_64-unknown-linux-musl-ld: cannot find -lgcc_s
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:1110: Gperf-simple] Error 1
make[1]: Leaving directory '/tmp/nix-build-libunwind-1.3.1-x86_64-unknown-linux-musl.drv-0/libunwind-1.3.1/tests'
make: *** [Makefile:598: all-recursive] Error 1
builder for '/nix/store/kr4iygd77ng6j01w4255wka01mwavf97-libunwind-1.3.1-x86_64-unknown-linux-musl.drv' failed with exit code 2
error: build of '/nix/store/kr4iygd77ng6j01w4255wka01mwavf97-libunwind-1.3.1-x86_64-unknown-linux-musl.drv' failed

Expected behavior

Default definition builds out-of-the-box, either directly or by reference as dependency.

Metadata

 - system: `"x86_64-linux"`
 - host os: `Linux 4.9.125-linuxkit`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.2.2`
 - channels(root): `"nixpkgs-20.03beta321.be346a1f4bd"`
 - nixpkgs: `/root/.nix-defexpr/channels/nixpkgs`

[FRidh]

Seems -lgcc_s needs to be replaced with -lgcc_eh in case of stdenv.hostPlatform.isMusl.

[FRidh]

fix in #83659