CMake: Clear CMAKE_REQUIRED_FLAGS before calling FindLAPACK

CMAKE_REQUIRED_FLAGS is populated by dealii with CXXFLAGS and this
should be cleared before calling any function that calls try_compile
on a C file. FindLAPACK calls FindTHREADS.cmake which uses try_compile
on a C file.

diff --git a/cmake/configure/configure_1_lapack.cmake b/cmake/configure/configure_1_lapack.cmake
index 2eb4519a15db4eb7af794ea904e578eeb407354b..b773ccbb8d1e41b2e5eafffac4d09e0818a626cd 100644 (file)
--- a/cmake/configure/configure_1_lapack.cmake
+++ b/cmake/configure/configure_1_lapack.cmake
@@ -18,6 +18,7 @@
 #
 
 MACRO(FEATURE_LAPACK_FIND_EXTERNAL var)
+  CLEAR_CMAKE_REQUIRED()
   FIND_PACKAGE(LAPACK)
 
   #