Fix in KPP compilation during integration edit to use correct make variable

[islas]

TYPE: bug fix

KEYWORDS: make, compilation

SOURCE: internal

DESCRIPTION OF CHANGES:
Problem:
PR #2018 introduced CMake compilation of the chem and KPP code. In order to do that certain helper programs created during the compilation process were reworked. The KPP mechanism integration edit program, integr_edit.exe was changed to take in explicit arguments for the files to read and write. However, the edits to the makefile that control this call use an invalid variable $(MODEL) where $(MECH) should be used instead.

Solution:
Use the appropriate $(MECH) variable to construct command line arguments to intergr_edit.exe

ISSUE:
#2216

TESTS CONDUCTED:

1. Recreated the issues noted in WRFCHEM fails to build with Intel OneAPI LLVM using old configure file #2216, though not limited to the intel compilers. Diagnosed as segfault due to reading of nonexistent file from null expansion of bad make variable. Fixed and recompiled successfully.

[weiwangncar]

The regression test results:

Test Type              | Expected  | Received |  Failed
= = = = = = = = = = = = = = = = = = = = = = = =  = = = =
Number of Tests        : 23           24
Number of Builds       : 60           57
Number of Simulations  : 158           150        0
Number of Comparisons  : 95           86        0

Failed Simulations are: 
None
Which comparisons are not bit-for-bit: 
None