SuiteSparse_config: Use configure result for whether to use clock_gettime

Use result of feature test to decide whether `clock_gettime` can be used.

Author: mmuetzel

SuiteSparse_config/Config/SuiteSparse_config.h.in

@@ -372,14 +372,13 @@ int SuiteSparse_divcomplex
     // but other packages can themselves use OpenMP.  In this case,
     // those packages should use omp_get_wtime() directly.  This can
     // be done via the SUITESPARSE_TIME macro, defined below:
+    #cmakedefine SUITESPARSE_HAVE_CLOCK_GETTIME
     #if defined ( _OPENMP )
         #define SUITESPARSE_TIMER_ENABLED
         #define SUITESPARSE_TIME (omp_get_wtime ( ))
-    #elif defined ( _POSIX_C_SOURCE )
-        #if _POSIX_C_SOURCE >= 199309L
+    #elif defined ( SUITESPARSE_HAVE_CLOCK_GETTIME )
         #define SUITESPARSE_TIMER_ENABLED
         #define SUITESPARSE_TIME (SuiteSparse_time ( ))
-        #endif
     #else
         // No timer is available
         #define SUITESPARSE_TIME (0)

SuiteSparse_config/SuiteSparse_config.c

@@ -495,7 +495,7 @@ void *SuiteSparse_free      /* always returns NULL */
         tic [1] = 0 ;
     }
 
-#else 
+#else
 
     /* ---------------------------------------------------------------------- */
     /* POSIX timer */
@@ -616,7 +616,7 @@ double SuiteSparse_hypot (double x, double y)
             r = x / y ;
             s = y * sqrt (1.0 + r*r) ;
         }
-    } 
+    }
     return (s) ;
 }
 

SuiteSparse_config/SuiteSparse_config.h

@@ -372,14 +372,13 @@ int SuiteSparse_divcomplex
     // but other packages can themselves use OpenMP.  In this case,
     // those packages should use omp_get_wtime() directly.  This can
     // be done via the SUITESPARSE_TIME macro, defined below:
+    #define SUITESPARSE_HAVE_CLOCK_GETTIME
     #if defined ( _OPENMP )
         #define SUITESPARSE_TIMER_ENABLED
         #define SUITESPARSE_TIME (omp_get_wtime ( ))
-    #elif defined ( _POSIX_C_SOURCE )
-        #if _POSIX_C_SOURCE >= 199309L
+    #elif defined ( SUITESPARSE_HAVE_CLOCK_GETTIME )
         #define SUITESPARSE_TIMER_ENABLED
         #define SUITESPARSE_TIME (SuiteSparse_time ( ))
-        #endif
     #else
         // No timer is available
         #define SUITESPARSE_TIME (0)