The configure test for mandatory -lm is broken, because the single
pow(a,b) call is optimized away. Fix this by forcing the call to be
compiled in via return statement.
This compiles without a change on amd64 and fixes the build on armv7.
Index: patches/patch-configure
===================================================================
RCS file: patches/patch-configure
diff -N patches/patch-configure
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ patches/patch-configure 26 Apr 2018 16:47:22 -0000
@@ -0,0 +1,16 @@
+$OpenBSD$
+
+Index: configure
+--- configure.orig
++++ configure
+@@ -4432,9 +4432,8 @@ cat >>conftest.$ac_ext <<_ACEOF
+ int
+ main ()
+ {
+-pow(a,b)
++return pow(a,b)
+ ;
+- return 0;
+ }
+ _ACEOF
+ rm -f conftest.$ac_objext conftest$ac_exeext
