Extended Description

echo "int foo(void) { return 0; }"> foo.c
echo "int foo(void); int main() {foo(); return 0;}">main.c

$ clang-7 -fuse-ld=lld -flto -O2 foo.c main.c -o foo
=> works fine

$ clang-8 -fuse-ld=lld -flto -O2 foo.c main.c -o foo
ld.lld: error: Invalid summary version 6, 1, 2, 3 or 4 expected
ld.lld: error: Invalid summary version 6, 1, 2, 3 or 4 expected
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Maybe it is intended but if this is the case, the error message should be improved