BUG #14022: Installer fails complaining about COMSPEC but COMSPEC is correct.

The following bug has been logged on the website:

Bug reference: 14022
Logged by: Mehmet Sinan Hasanoglu
Email address: shasanoglu(at)gmail(dot)com
PostgreSQL version: 9.5.1
Operating system: Windows 7 64 bit
Description:

I checked comspec and it is correct. I double checked with

%COMSPEC%" /C "echo test ok

and everything seems ok. However installer (both 32 bit and 64 bit) fails
with the message:

There has been an error.
The environment variable COMSPEC does not seem to point the cmd.exe or there
is a trailing semicolon present. Please fix this variable and restart
installation.

I am attaching the installer log too:

Log started 03/15/2016 at 10:37:37
Preferred installation mode : qt
Trying to init installer in mode qt
Mode qt successfully initialized
Executing D:\TEMP/postgresql_installer_79c6abfe43/temp_check_comspec.bat
Script exit code: 1

Script output:

Script stderr:
'"D:\TEMP\POSTGR~1\TEMP_C~1.BAT"' is not recognized as an internal or
external command,
operable program or batch file.

Error running D:\TEMP/postgresql_installer_79c6abfe43/temp_check_comspec.bat
: '"D:\TEMP\POSTGR~1\TEMP_C~1.BAT"' is not recognized as an internal or
external command,
operable program or batch file.