Not sure whether anyone cares about supporting ancient Linux versions... But RHEL 5.x shipped with librsvg2 2.16.1, which did not provide the LIBSRVG_CHECK_VERSION macro.
Simple patch below allows Emacs 26.3 to compile on RHEL/CentOS 5.
- Pat
diff -u -r emacs-26.3-orig/src/image.c emacs-26.3/src/image.c
--- emacs-26.3-orig/src/image.c 2019-06-12 03:50:42.000000000 -0700
+++ emacs-26.3/src/image.c 2019-08-29 10:13:13.000000000 -0700
@@ -9313,9 +9313,11 @@
#if GNUC_PREREQ (4, 6, 0)
#pragma GCC diagnostic push
#endif
+ #if defined(LIBSRVG_CHECK_VERSION)
#if LIBRSVG_CHECK_VERSION (2, 45, 1) && GNUC_PREREQ (4, 2, 0)
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#endif
+ #endif
/* Parse the contents argument and fill in the rsvg_handle. */
rsvg_handle_write (rsvg_handle, (unsigned char *) contents, size, &err);