pulseaudio configure fails

[jghub]

upgrade fails. from the config.log:

   2299 configure:10349: checking whether C compiler accepts -std=gnu11
   2300 configure:10369: /usr/bin/clang -c -pipe -Os -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk -arch x86_64 -pedantic -Werror -std=gnu11 -I/opt/local/include -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk conftest.c >&5
   2301 conftest.c:74:9: error: '_DARWIN_C_SOURCE' macro redefined [-Werror,-Wmacro-redefined]
   2302 #define _DARWIN_C_SOURCE 200112L
   2303         ^
   2304 conftest.c:50:9: note: previous definition is here
   2305 #define _DARWIN_C_SOURCE 1
   2306         ^
   2307 1 error generated. 

as ryan schmidt explained to me on the mailing list:

"The configure test fails to do what it was trying to do because it redefines a macro, which is usually accepted with a warning, but it requests that warnings be turned into errors by using -Werror.

autoconf 2.71 caused this problem to appear. autoconf 2.69 didn't first define _DARWIN_C_SOURCE to 1 but autoconf 2.71 does.

The autoconf 2.70 release notes specifically state that "Running configure tests with warnings promoted to errors is not supported."

observed with OSX 10.15.7

[jmroot (Joshua Root)]

In 7e627d606e6c1334a1c69775baeb4a97c18e24f9/macports-ports (master):

pulseaudio: fix C11 detection

Closes: #62433