Bug#926772: underlinked clang libraries on armel cause build failures

[Matthias Klose]

Package: src:llvm-toolchain-7
Version: 1:7.0.1-8
Severity: serious
Tags: sid buster

underlinked clang libraries on armel cause build failures, as seen at
https://buildd.debian.org/status/package.php?p=creduce

/usr/bin/ld:
/usr/lib/llvm-7/lib/libclangFrontend.a(SerializedDiagnosticReader.cpp.o):
undefined reference to symbol '__atomic_load_4@@LIBATOMIC_1.0'
/usr/bin/ld: //usr/lib/arm-linux-gnueabi/libatomic.so.1: error adding symbols:
DSO missing from command line
collect2: error: ld returned 1 exit status
make[4]: *** [Makefile:868: clang_delta] Error 1

this prevents migration of creduce to testing/buster.