Bug 1491999: Quote command line for multiple components. r=mhowell

The macro expansion of ExecAndWaitForInputIdle consumes the quotes
around the macro argument. The argument has an extra layer of quotes
around the executable name, which keeps it together even if it has
spaces, but we need yet another layer around the whole command line or
else each component of the command line appears as another argument to
StrCpy.

Standard practice is to quote args in the macro definition, I overlooked
this in the initial implementation.

Differential Revision: https://phabricator.services.mozilla.com/D6111

toolkit/mozapps/installer/windows/nsis/common.nsh

@@ -8132,7 +8132,7 @@
   Push $2
 
   ; Command line
-  StrCpy $0 ${CMDLINE}
+  StrCpy $0 "${CMDLINE}"
 
   ; STARTUPINFO
   System::Alloc 68