Dynamically load libpulse.so.0 and libasound.so.1 on Linux

By generating stubs using https://github.com/hpvb/dynload-wrapper we
can dynamically load libpulse and libasound on systems where it is available.
Both are still a build-time requirement but no longer a run-time dependency.

For maintenance purposes the wrappers should not need to be re-generated
unless we want to bump pulse or asound to an incompatible version. It is
unlikely we will want to do this any time soon.

This closes #20978

platform/linuxbsd/detect.py

@@ -310,9 +310,8 @@ def configure(env):
 
     if os.system("pkg-config --exists alsa") == 0:  # 0 means found
         print("Enabling ALSA")
+        env["alsa"] = True
         env.Append(CPPDEFINES=["ALSA_ENABLED", "ALSAMIDI_ENABLED"])
-        # Don't parse --cflags, we don't need to add /usr/include/alsa to include path
-        env.ParseConfig("pkg-config alsa --libs")
     else:
         print("ALSA libraries not found, disabling driver")
 
@@ -320,7 +319,7 @@ def configure(env):
         if os.system("pkg-config --exists libpulse") == 0:  # 0 means found
             print("Enabling PulseAudio")
             env.Append(CPPDEFINES=["PULSEAUDIO_ENABLED"])
-            env.ParseConfig("pkg-config --cflags --libs libpulse")
+            env.ParseConfig("pkg-config --cflags libpulse")
         else:
             print("PulseAudio development libraries not found, disabling driver")