Use pkg-config if available

Co-authored-by: Alexander Richardson <[email protected]>
Signed-off-by: Tim Hutt <[email protected]>

cmake/modules/FindGMP.cmake

@@ -9,25 +9,34 @@
 #  GMP_CXX_LIBRARIES - LIST:The libraries needed to use GMP via it's C++ interface
 
 include(FindPackageHandleStandardArgs)
+find_package(PkgConfig)
+if(PKG_CONFIG_FOUND)
+  pkg_check_modules(PC_GMP QUIET gmp)
+  pkg_check_modules(PC_GMPXX QUIET gmpxx)
+endif()
 
 # Try to find libraries
 find_library(GMP_C_LIBRARIES
   NAMES gmp
+  PATHS ${PC_GMP_LIBRARY_DIRS}
   DOC "GMP C libraries"
 )
 find_library(GMP_CXX_LIBRARIES
   NAMES gmpxx
+  PATHS ${PC_GMPXX_LIBRARY_DIRS}
   DOC "GMP C++ libraries"
 )
 
 # Try to find headers
 find_path(GMP_C_INCLUDES
   NAMES gmp.h
+  PATHS ${PC_GMP_INCLUDE_DIRS}
   DOC "GMP C header"
 )
 
 find_path(GMP_CXX_INCLUDES
   NAMES gmpxx.h
+  PATHS ${PC_GMPXX_INCLUDE_DIRS}
   DOC "GMP C++ header"
 )