hunter: add option WITH_OPENBLAS providing LAPACK for ceres

OpenBLAS is expected to be built with LAPACK support.

Change-Id: I978ad27eb02ac0562eb97913a4fdb4d975df2b20

CMakeLists.txt

@@ -134,6 +134,7 @@ endif()
 # language definition.
 option(USE_CUDA "Enable use of CUDA linear algebra solvers." ON)
 option(LAPACK "Enable use of LAPACK directly within Ceres." ON)
+option(WITH_OPENBLAS "Build against OpenBLAS providing BLAS/LAPACK to use directly within Ceres." OFF)
 # Template specializations for the Schur complement based solvers. If
 # compile time, binary size or compiler performance is an issue, you
 # may consider disabling this.
@@ -276,6 +277,13 @@ if (NOT USE_CUDA)
   list(APPEND CERES_COMPILE_OPTIONS CERES_NO_CUDA)
 endif (NOT USE_CUDA)
 
+if (WITH_OPENBLAS)
+  hunter_add_package(OpenBLAS)
+  find_package(OpenBLAS CONFIG REQUIRED)
+  message("-- Found OpenBLAS library providing BLAS and LAPACK functionality")
+  set(LAPACK_FOUND ON)
+  set(LAPACK_LIBRARIES OpenBLAS::OpenBLAS)
+else ()
 if (LAPACK)
   hunter_add_package(LAPACK)
   find_package(LAPACK CONFIG QUIET)
@@ -292,6 +300,7 @@ else (LAPACK)
   message("-- Building without LAPACK.")
   list(APPEND CERES_COMPILE_OPTIONS CERES_NO_LAPACK)
 endif (LAPACK)
+endif()
 
 # Set the install path for the installed CeresConfig.cmake configuration file
 # relative to CMAKE_INSTALL_PREFIX.