Revert "return correct path for Sys.executablePath() when in macro (closes #3401)"

This reverts commit 8ee14ca6a00673e421ae87a895e614f329d9e44e.
Revert "fix Sys.command for windows: always escape cmd, wrap resulting command in quotes before executing (see #3402)"

This reverts commit c0406cc928c71657284c9872415c6bd5b22b000e.