https://github.com/icculus/SDL_sound/pull/80

From 83f33e04125517197520e26452d06b81c2d7b429 Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Sat, 12 Nov 2022 02:49:21 +0000
Subject: [PATCH] Fix underlinking with lld (missing -lm)

We need to explicitly search for and link with -lm if needed by
libc for math libraries like `log` and `sin`:
```
ld.lld: error: undefined reference due to --no-allow-shlib-undefined: sin
>>> referenced by ../.libs/libSDL_sound.so

ld.lld: error: undefined reference due to --no-allow-shlib-undefined: log
>>> referenced by ../.libs/libSDL_sound.so
```

It turns out Gentoo has actually had a patch for this since 2012 (mea
culpa!) but it never made its way upstream.

We're already using libtool, so just use the macro it provides for
this purpose.

Signed-off-by: Sam James <sam@gentoo.org>
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,7 +12,7 @@ endif
 SDLSOUND_HDRS = SDL_sound.h
 SDLSOUND_SRCS = SDL_sound.c SDL_sound_internal.h alt_audio_convert.c alt_audio_convert.h audio_convert.c
 SDLSOUND_LDFLAGS = -no-undefined -release $(LT_RELEASE) -version-info $(LT_CURRENT):$(LT_REVISION):$(LT_AGE)
-SDLSOUND_LIBADD = decoders/libdecoders.la $(TIMIDITY_LIB)
+SDLSOUND_LIBADD = decoders/libdecoders.la $(TIMIDITY_LIB) $(LIBM)
 
 if USE_SDL2
 lib_LTLIBRARIES = libSDL2_sound.la
--- a/configure.ac
+++ b/configure.ac
@@ -54,6 +54,7 @@ AC_PROG_CC
 AC_PROG_INSTALL
 AC_PROG_LN_S
 LT_INIT([win32-dll])
+LT_LIB_M
 PKG_PROG_PKG_CONFIG