Backport upstream fix for MPI patch

debian/patches/0001-Fix-cross-compilation-with-MPI.patch

@@ -8,14 +8,14 @@ Forwarded: https://gitlab.kitware.com/cmake/cmake/-/merge_requests/6537
  1 file changed, 35 insertions(+), 1 deletion(-)
 
 diff --git a/Modules/FindMPI.cmake b/Modules/FindMPI.cmake
-index d8f0334..f7faa54 100644
+index d8f0334..1aaba43 100644
 --- a/Modules/FindMPI.cmake
 +++ b/Modules/FindMPI.cmake
 @@ -267,6 +267,7 @@ cmake_policy(PUSH)
  cmake_policy(SET CMP0057 NEW) # if IN_LIST
  
  include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
-+include(${CMAKE_CURRENT_LIST_DIR}/FindPkgConfig.cmake)
++find_package(PkgConfig QUIET)
  
  # Generic compiler names
  set(_MPI_C_GENERIC_COMPILER_NAMES          mpicc    mpcc      mpicc_r mpcc_r)
@@ -34,7 +34,7 @@ index d8f0334..f7faa54 100644
 +          else()
 +            set(_MPI_PKG "")
 +          endif()
-+          if(_MPI_PKG)
++          if(_MPI_PKG AND PKG_CONFIG_FOUND)
 +            pkg_check_modules("MPI_${LANG}_PKG" "${_MPI_PKG}")
 +            if("${MPI_${LANG}_PKG_FOUND}")
 +              set(MPI_${LANG}_COMPILE_OPTIONS  ${MPI_${LANG}_PKG_CFLAGS}        CACHE STRING "MPI ${LANG} compilation options"       FORCE)