Fix installation on VC-WIN32 with nmake

Commit b8326569 fixed whitespace handling in the copy script, which
exposes bugs in the install routine for nmake Makefiles.

This corrects the quoting around the copy invocation for the openssl.exe
binary.

CLA: trivial

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3942)