improvements support for sysroot

sysroot library support sometimes does not work


```

cat > 1.c << \!
int foo() { return 0; }
!

cat > 2.c << \!
int bar() { return 0; }
!

rm -f lib2.* && clang -c -target x86_64 -c 2.c
ld.eld -shared 2.o -o lib2.so
clang -c -target x86_64 -c 1.c
ld.eld --sysroot=/tmp/ -Bdynamic 1.o -L. =lib2.so -o a --reproduce a.tar
```

Error output :

`Fatal: cannot read file '=lib2.so'`
