portable mingw/msys

Hi, 
I am trying to install mingw/msys (bash, autotools, and compilers)on one machine and use the installation on other machines. The only part I am stuck at is
In the /etc/fstab file it has
<windows installation path to mingw> /mingw 
For my use-case <windows installation path to mingw> is not fixed. What is fixed is mingw can be reached by ../.. from msys, and $MINGWPATH environment variable pointing to mingw path. 
/mingw/.. path is hard-wired in almost all the autotools scripts.
Also, using a parameter such as $MINGWPATH in /etc/fstab doesn't work. 

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