Merge #2357: [build] Allow export of environ symbols

32473aa build: Allow export of environ symbols (Wladimir J. van der Laan)

Pull request description:

  This export was introduced in #2278 which added
  ```
  //! Necessary on some platforms
  extern char** environ;
  ```

  Which is one of the causes of the current broken gitian build.

  Coming from f6e4225

ACKs for top commit:
  random-zebra:
    utACK 32473aa
  Fuzzbawls:
    utACK 32473aa

Tree-SHA512: 3091cdbccb9c8d90a1459479d41d8205a90ccb023a53836c8bc9d84af0c4dce0ce93f174b5b1c19af1f4496839ff48f33dae1124ccdbb2056fad4e1e1de406d8

contrib/devtools/symbol-check.py

@@ -47,7 +47,8 @@
 
 # Ignore symbols that are exported as part of every executable
 IGNORE_EXPORTS = {
-'_edata', '_end', '__end__', '_init', '__bss_start', '__bss_start__', '_bss_end__', '__bss_end__', '_fini', '_IO_stdin_used', 'stdin', 'stdout', 'stderr'
+'_edata', '_end', '__end__', '_init', '__bss_start', '__bss_start__', '_bss_end__', '__bss_end__', '_fini', '_IO_stdin_used', 'stdin', 'stdout', 'stderr',
+'environ', '_environ', '__environ',
 }
 READELF_CMD = os.getenv('READELF', '/usr/bin/readelf')
 CPPFILT_CMD = os.getenv('CPPFILT', '/usr/bin/c++filt')