glibc: Create the ld.so symlink first
glibc: Create the ld.so symlink first

So that if later steps of the postinstall fails, this
critical step has completed.

rwhogg/homebrew-core,Linuxbrew/homebrew-core,rwhogg/homebrew-core,LinuxbrewTestBot/homebrew-core,Linuxbrew/homebrew-core,maxim-belkin/homebrew-core,LinuxbrewTestBot/homebrew-core,maxim-belkin/homebrew-core