FindPETSc.cmake: search for petscconf.h

Relevant file: FindPETSc.cmake:L103

This cmake find module search for petscconf.h in ${PETSC_DIR}/include/ but in some case this file is not exactly in this directory.

Example:
On Plafrim, if you load the module linalg/petsc/3.8.3 PETSc is installed under /cm/shared/dev/apps/linalg/petsc/3.8.3/gcc/7.3.0/openmpi/3.0.0/mkl/2018.0.015 and petscconf.h is under linux-gnu-c/include/ or arch-linux2-c-opt/include/.

It seems that it depend of PETSc version.

Relevant CMake error:

 CMake Error at cmake/morse_cmake/FindPETSc.cmake:102 (message):
   include/petscconf.h not found in PETSC_DIR =
   /cm/shared/dev/apps/linalg/petsc/3.8.3/gcc/7.3.0/openmpi/3.0.0/mkl/2018.0.015
 Call Stack (most recent call first):
   cmake/lib-finding.cmake:173 (find_package)
   CMakeLists.txt:10 (include)

Is it possible to search in more path for this file ? For example with find_path() ?