Improve ./configure script to fix macOS function detection issues

configure.ac

@@ -1839,14 +1839,12 @@ if test "$have_armv7apmccntr"x = "yes"x; then
 fi
 
 # Check if we have native exp10 and exp10f functions. If not fallback to our
-# implementations. On Apple/CLANG we have __exp10, so also check for that
+# implementations. On Apple/CLANG/Homebrew gcc we have __exp10, so also check for that
 # if the compiler is clang.
 AC_CHECK_LIB([m],[exp10], [AC_DEFINE([HAVE_EXP10],1,[The exp10 function is present.])])
 AC_CHECK_LIB([m],[exp10f], [AC_DEFINE([HAVE_EXP10F],1,[The exp10f function is present.])])
-if test "$ax_cv_c_compiler_vendor" = "clang"; then
 AC_CHECK_LIB([m],[__exp10], [AC_DEFINE([HAVE___EXP10],1,[The __exp10 function is present.])])
 AC_CHECK_LIB([m],[__exp10f], [AC_DEFINE([HAVE___EXP10F],1,[The __exp10f function is present.])])
-fi
 
 # Check if we have native sincos and sincosf functions. If not fallback to our
 # implementations. On Apple/CLANG we have __sincos, so also check for that
@@ -1858,6 +1856,14 @@ if test "$ax_cv_c_compiler_vendor" = "clang"; then
       AC_CHECK_LIB([m],[__sincosf], [AC_DEFINE([HAVE___SINCOSF],1,[The __sincosf function is present.])])
 fi
 
+# On Apple (CLANG or Homebrew gcc), check for __sincos and __sincosf inline functions in the headers.
+AC_CHECK_HEADERS([math.h], [
+  AC_CHECK_DECLS([__sincos, __sincosf], [
+    AC_DEFINE([HAVE___SINCOS], 1, [The __sincos function is present.])
+    AC_DEFINE([HAVE___SINCOSF], 1, [The __sincosf function is present.])
+  ], [], [#include <math.h>])
+])
+
 # The aocc compiler has optimized maths libraries that we should use. Check
 # any clang for this support. Note do this after the basic check for maths
 # as we need to make sure -lm follows. Also note needs -Ofast or -ffast-math

src/feedback/GEAR/initial_mass_function.c

@@ -19,6 +19,7 @@
 
 /* local headers */
 #include "initial_mass_function.h"
+#include "exp10.h"
 
 #include "hdf5_functions.h"
 #include "stellar_evolution_struct.h"

src/feedback/GEAR/stellar_evolution.c

@@ -28,6 +28,7 @@
 #include "stellar_evolution_struct.h"
 #include "supernovae_ia.h"
 #include "supernovae_ii.h"
+#include "exp10.h"
 
 #include <math.h>
 #include <stddef.h>