Dockerfile.arm: fix ldd from crosstool-ng
Dockerfile.arm: fix ldd from crosstool-ng

Make ldd from crosstool-ng to output tab instead of whitespace
when listing the libraries. So it is consistent to the behavior
of native ldd. This restores the function of `brew linkage`.

[ci skip]

xu-cheng/homebrew-portable,Homebrew/homebrew-portable