Don't check all libraries, use AS_IF.

Fix AC_ARG_WITH usage to be like the manual suggests:
https://autotools.io/autoconf/arguments.html

configure.ac

@@ -112,11 +112,12 @@ case $host in
   AC_CHECK_LIB(jack, jack_client_open, , AC_MSG_ERROR(JACK support requires the jack library!))], )
 
   # Look for ALSA flag
-  AC_ARG_WITH(alsa, [  --with-alsa = choose native ALSA sequencer API support (linux only)], [
+  AC_ARG_WITH(alsa, [  --with-alsa = choose native ALSA sequencer API support (linux only)])
+  AS_IF([test "x$with_alsa" == "xyes"], [
     api="$api -D__LINUX_ALSA__"
     req="$req alsa"
     AC_MSG_RESULT(using ALSA)
-    AC_CHECK_LIB(asound, snd_seq_open, , AC_MSG_ERROR(ALSA support requires the asound library!))], )
+    AC_CHECK_LIB(asound, snd_seq_open, , AC_MSG_ERROR(ALSA support requires the asound library!))])
 
   if [test "$api" == "";] then
     AC_MSG_RESULT(using ALSA)
@@ -136,11 +137,12 @@ case $host in
   AC_CHECK_LIB(jack, jack_client_open, , AC_MSG_ERROR(JACK support requires the jack library!))], )
 
   # Look for Core flag
-  AC_ARG_WITH(core, [  --with-core = choose CoreMidi API support (mac only)], [
+  AC_ARG_WITH(core, [  --with-core = choose CoreMidi API support (mac only)])
+  AS_IF([test "x$with_core" == "xyes"], [
     api="$api -D__MACOSX_CORE__"
     AC_MSG_RESULT(using CoreMidi)
     AC_CHECK_HEADER(CoreMIDI/CoreMIDI.h, [], [AC_MSG_ERROR(CoreMIDI header files not found!)] )
-    LIBS="$LIBS -framework CoreMIDI -framework CoreFoundation -framework CoreAudio" ], )
+    LIBS="$LIBS -framework CoreMIDI -framework CoreFoundation -framework CoreAudio" ])
 
   # If no api flags specified, use CoreMidi
   if [test "$api" == ""; ] then
@@ -155,15 +157,17 @@ case $host in
 
   *-mingw32*)
   # Look for WinMM flag
-  AC_ARG_WITH(winmm, [  --with-winmm = choose Windows MultiMedia (MM) API support (windoze only)], [
+  AC_ARG_WITH(winmm, [  --with-winmm = choose Windows MultiMedia (MM) API support (windoze only)])
+  AS_IF([test "x$with_winmm" == "xyes"], [
     api="$api -D__WINDOWS_MM__"
     AC_MSG_RESULT(using WinMM)
-    AC_SUBST( LIBS, [-lwinmm] )], )
+    AC_SUBST( LIBS, [-lwinmm] )])
 
-  AC_ARG_WITH(winks, [  --with-winks = choose kernel streaming support (windoze only)], [
+  AC_ARG_WITH(winks, [  --with-winks = choose kernel streaming support (windoze only)])
+  AS_IF([test "x$with_winks" == "xyes"], [
     api="$api -D__WINDOWS_KS__"
     AC_SUBST( LIBS, ["-lsetupapi -lksuser"] )
-    AC_MSG_RESULT(using kernel streaming) ], )
+    AC_MSG_RESULT(using kernel streaming) ])
 
   # I can't get the following check to work so just manually add the library
 	# or could try the following?  AC_LIB_WINMM([midiOutGetNumDevs])