[gcc r11-5217] Include math.h in nextafter-2.c test.

[Michael Meissner <meissner@gcc.gnu.org>]

https://gcc.gnu.org/g:81a3f3d1b6fecc10ba8c460644dfb9ebabbb9eec

commit r11-5217-g81a3f3d1b6fecc10ba8c460644dfb9ebabbb9eec
Author: Michael Meissner <meissner@linux.ibm.com>
Date:   Fri Nov 20 18:34:24 2020 -0500

    Include math.h in nextafter-2.c test.
    
    Since the test is compiled with -fno-builtin, include math.h to allow for
    implementations (like the PowerPC) that have multiple versions of long double
    that are selectable by switch.  Math.h could possibly switch what function
    nextafterl points to.
    
    gcc/testsuite/
    2020-11-17  Michael Meissner  <meissner@linux.ibm.com>
    
            * gcc.dg/nextafter-2.c: Include math.h.

Diff:
---
 gcc/testsuite/gcc.dg/nextafter-2.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/nextafter-2.c b/gcc/testsuite/gcc.dg/nextafter-2.c
index e51ae94be0c..8149a709fa5 100644
--- a/gcc/testsuite/gcc.dg/nextafter-2.c
+++ b/gcc/testsuite/gcc.dg/nextafter-2.c
@@ -6,6 +6,18 @@
 
 #include <stdlib.h>
 
+/* In order to run on systems like the PowerPC that have 3 different long
+   double types, include math.h so it can choose what is the appropriate
+   nextafterl function to use.
+
+   If we didn't use -fno-builtin for this test, the PowerPC compiler would have
+   changed the names of the built-in functions that use long double.  The
+   nextafter-1.c function runs with this mapping.
+
+   Since this test uses -fno-builtin, include math.h, so that math.h can make
+   the appropriate choice to use.  */
+#include <math.h>
+
 #if defined(__GLIBC__) && defined(__GLIBC_PREREQ)
 # if !__GLIBC_PREREQ (2, 24)
 /* Workaround buggy nextafterl in glibc 2.23 and earlier,