Add INNO_ARGS makefile var for signtool

[musm]

@staticfloat

Signing now works when I add the following to my Make.user

override INNO_ARGS=/Dsign=true "/Smysigntool=\$$q`cygpath -w /cygdrive/c/Program\ Files\ \(x86\)/Windows\ Kits/10/bin/10.0.19041.0/x64/signtool.exe`\$$q sign /f \$$q`cygpath -w /cygdrive/c/Users/Mus/Code/julia/mycert.pfx`\$$q /p Pass123 \$$f"

In simplified terms

override INNO_ARGS=/Dsign=true "/Smysigntool=\$$q`cygpath -w {{signtool path}}`\$$q sign /f \$$q`cygpath -w {{certificate path}}`\$$q /p {{certificate password}} \$$f"

Yes it's kind of a total mess, but we can't help it since this is going through like 3 layers of path/filename translations: makefiles, cygwin, and inno....

[staticfloat]

Great! This is perfect.

[musm]

Great. BTW do these makefile vars default to empty strings if not defined? I was contemplating whether we needed to define them in Make.inc

[staticfloat]

Yes, they default to empty.