Corrected a typo in mklib

[Iximiel]

Description

Mklib now deletes correctly all the tmpfile:

I have changed back:

• tmpfile=$(mktemp ${file%.cpp}.XXXXXX).cpp that creates a tmpfile WITHOUT the .cpp extension, but saves tmpfile with the .cpp extension to be manipulated by the script
  into:
• tmpfile=$(mktemp ${file%.cpp}.XXXXXX.cpp) creates a tmp .cpp file that will be correctly deleted after

This patch was though for the single file mklib, and we must note that do NOT patch an eventual header file with the old paths in it

Target release

I would like my code to appear in the next 2.9 patch /in 2.10

Type of contribution

• changes to code or doc authored by PLUMED developers, or additions of code in the core or within the default modules
• changes to a module not authored by you
• new module contribution or edit of a module authored by you

Copyright

• I agree to transfer the copyright of the code I have written to the PLUMED developers or to the author of the code I am modifying.

• the module I added or modified contains a COPYRIGHT file with the correct license information. Code should be released under an open source license. I also used the command cd src && ./header.sh mymodulename in order to make sure the headers of the module are correct.

Tests

• I added a new regtest or modified an existing regtest to validate my changes.
• I verified that all regtests are passed successfully on GitHub Actions.

[GiovanniBussi]

On my computer, the file is named pippo.XXXXXX.cpp literally: XXXXXX is not replaced with a number. This is consistent with the documentation:

     The mktemp utility takes each of the given file name templates and overwrites a portion of it to create a file name.  This file name is unique and suitable
     for use by the application.  The template may be any file name with some number of ‘Xs’ appended to it, for example /tmp/temp.XXXX.  The trailing ‘Xs’ are
     replaced with the current process number and/or a unique letter combination.  The number of unique file names mktemp can return depends on the number of

[GiovanniBussi]

More discussion here

[Iximiel]

So as usual I fallen for the trap of gnu/linux doing things more permissive than the standard. I'm pushing the workaround in minutes