build with Meson instead of autotools

So long, autotools!  This is my last MPD related project to migrate
away from it.  It has its strengths, but also very obvious weaknesses
and weirdnesses.  Today, many of its quirks are not needed anymore,
and are cumbersome and slow.  Now welcome our new Meson overlords!

python/build/cmdline.py

@@ -1,29 +0,0 @@
-def concatenate_cmdline_variables(src, names):
-    """Find duplicate variable declarations on the given source list, and
-    concatenate the values of those in the 'names' list."""
-
-    # the result list being constructed
-    dest = []
-
-    # a map of variable name to destination list index
-    positions = {}
-
-    for item in src:
-        i = item.find('=')
-        if i > 0:
-            # it's a variable
-            name = item[:i]
-            if name in names:
-                # it's a known variable
-                if name in positions:
-                    # already specified: concatenate instead of
-                    # appending it
-                    dest[positions[name]] += ' ' + item[i + 1:]
-                    continue
-                else:
-                    # not yet seen: append it and remember the list
-                    # index
-                    positions[name] = len(dest)
-        dest.append(item)
-
-    return dest

python/build/meson.py

@@ -40,6 +40,7 @@ c = '%s'
 cpp = '%s'
 ar = '%s'
 strip = '%s'
+pkgconfig = '%s'
 %s
 
 [properties]
@@ -60,6 +61,7 @@ cpu_family = '%s'
 cpu = '%s'
 endian = '%s'
             """ % (toolchain.cc, toolchain.cxx, toolchain.ar, toolchain.strip,
+                   toolchain.pkg_config,
                    windres,
                    toolchain.install_prefix,
                    repr((toolchain.cppflags + ' ' + toolchain.cflags).split()),