jq does not build with Xcode 12.0.1 on macOS 10.15 (darwin/19.6.0)

[tgyurci (Teubel György)]

After upgrading to latest Xcode jq failed to build:

src/builtin.c:194:31: error: implicit declaration of function 'lgamma_r' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  jv ret = JV_ARRAY(jv_number(lgamma_r(jv_number_value(input), &sign)));

Applying the already present patch from patch-src-builtin.c eliminates the error and jq complies successfully.

System info:

DEBUG: macOS 10.15 (darwin/19.6.0) arch i386                                                                                                          
DEBUG: MacPorts 2.6.3                                                                                                                                 
DEBUG: Xcode 12.0.1                                                                                                                                   
DEBUG: SDK 10.15
DEBUG: MACOSX_DEPLOYMENT_TARGET: 10.15

[chrstphrchvz (Christopher Chavez)]

PR opened: ​https://github.com/macports/macports-ports/pull/8870

[danchr (Dan Villiom Podlaski Christiansen)]

In 05ec0097df09635392ab134d8fa7ea7304160643/macports-ports (master):

jq: fix build with Xcode 12

The jq configure system checks whether lgamma_r() is defined in
libm, but not whether it is actually declared. On macOS, that is not
the case unless _REENTRANT was defined prior to including math.h.
Xcode 12 changed the defaults, so that using an undefined symbol gives
a hard error, breaking the build.

I had only run into this when building on an unreleased OS, but the
error is actually specific to Xcode 12. This adjusts the builtin patch
to address root cause, rather than just bypassing it, and applies the
patch universally.

Fixes: #61354
Closes: ​https://github.com/macports/macports-ports/pull/8870