compositor: add fallback strchrnul()

Android does not have this function.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
diff --git a/configure.ac b/configure.ac
index 7dbd9f9..ce97486 100644
--- a/configure.ac
+++ b/configure.ac
@@ -27,7 +27,7 @@
 
 AC_CHECK_HEADERS([execinfo.h])
 
-AC_CHECK_FUNCS([mkostemp])
+AC_CHECK_FUNCS([mkostemp strchrnul])
 
 PKG_CHECK_MODULES(COMPOSITOR,
 		  [wayland-server egl >= 7.10 glesv2 xkbcommon pixman-1])
diff --git a/shared/os-compatibility.c b/shared/os-compatibility.c
index 66934a8..21d4d02 100644
--- a/shared/os-compatibility.c
+++ b/shared/os-compatibility.c
@@ -168,3 +168,13 @@
 
 	return fd;
 }
+
+#ifndef HAVE_STRCHRNUL
+char *
+strchrnul(const char *s, int c)
+{
+	while (*s && *s != c)
+		s++;
+	return (char *)s;
+}
+#endif
diff --git a/shared/os-compatibility.h b/shared/os-compatibility.h
index b2021f1..c1edcfb 100644
--- a/shared/os-compatibility.h
+++ b/shared/os-compatibility.h
@@ -46,4 +46,9 @@
 int
 os_create_anonymous_file(off_t size);
 
+#ifndef HAVE_STRCHRNUL
+char *
+strchrnul(const char *s, int c);
+#endif
+
 #endif /* OS_COMPATIBILITY_H */