cpackget: path problem when installing local packs

[ReinhardKeil]

cpackget adds the wrong path when drive letter on windows is not specified

To Reproduce
Steps to reproduce the behavior:

1. checkout https://github.com/Open-CMSIS-Pack/csolution-examples and https://github.com/Open-CMSIS-Pack/pack-examples to these Windows directories:
   c:\w\csolution-examples
c:\w\pack-examples
2. set cd c:\w\csolution-examples as current directory
3. use cpackget add \w\pack-examples\STM32U5xx_DFP\Keil.STM32U5xx_DFP.pdsc

cpackget list now outputs:

`E: Keil.STM32U5xx_DFP@3.0.0-dev0 (installed via C:\w\csolution-examples\CubeMX\w\pack-examples\STM32U5xx_DFP\Keil.STM32U5xx_DFP.pdsc ) - error: open C:\w\csolution-examples\CubeMX\w\pack-examples\STM32U5xx_DFP\Keil.STM32U5xx_DFP.pdsc: The system cannot find the path specified.

Expected behavior
The path is correctly installed as

`I: Keil.STM32U5xx_DFP@3.0.0-dev0 (installed via C:\w\pack-examples\STM32U5xx_DFP\Keil.STM32U5xx_DFP.pdsc)

Environment:

• Windows 10
• cpackget 2.1.1

[ReinhardKeil]

Adding to this problem: c: works, whereas C: reports an issue (see below).

>cpackget add c:\w\pack-examples\STM32U5xx_DFP\Keil.STM32U5xx_DFP.pdsc  
I: Adding pdsc "c:\w\pack-examples\STM32U5xx_DFP\Keil.STM32U5xx_DFP.pdsc"

C:\w\csolution-examples>cpackget add C:\w\pack-examples\STM32U5xx_DFP\Keil.STM32U5xx_DFP.pdsc  
I: Adding pdsc "C:\w\pack-examples\STM32U5xx_DFP\Keil.STM32U5xx_DFP.pdsc"
W: Found PDSC file with an equal but malformed path (using '\'). Correcting entry and reinstalling.

[jkrech]

It now works for both lower and upper case drive letters (c:\ and C:\)