formula_installer: set `HOMEBREW_RELOCATE_RPATHS`
formula_installer: set `HOMEBREW_RELOCATE_RPATHS`

This enables `RPATH` relocation upon pouring bottles.

Part of #11329.

nandub/brew,MikeMcQuaid/brew,Homebrew/brew,MikeMcQuaid/brew,Homebrew/brew,nandub/brew,JCount/brew,claui/brew,MikeMcQuaid/brew,claui/brew,MikeMcQuaid/brew,claui/brew,Homebrew/brew,JCount/brew,EricFromCanada/brew,nandub/brew,EricFromCanada/brew,Homebrew/brew,EricFromCanada/brew,claui/brew,JCount/brew,EricFromCanada/brew,JCount/brew,nandub/brew