cmake: use FindALSA.cmake to find ALSA library

configure

@@ -677,6 +677,7 @@ ENABLE_STATIC_TRUE
 ENABLE_SHARED_FALSE
 ENABLE_SHARED_TRUE
 PKGCONFIG_LIBS_PRIV
+PKGCONFIG_DEPENDS
 SDL_RLD_FLAGS
 SDL_STATIC_LIBS
 SDL_LIBS
@@ -29873,6 +29874,8 @@ done
 
 
 
+PKGCONFIG_DEPENDS=""
+
 if test x$enable_shared = xyes; then
     PKGCONFIG_LIBS_PRIV="
 Libs.private:"