Merge bitcoin#17569: build: Allow export of environ symbols and work …

…around rv64 toolchain issue

eafd259 build: Add NX workaround for RV64 (Wladimir J. van der Laan)
f6e4225 build: Allow export of environ symbols (Wladimir J. van der Laan)

Pull request description:

  This export was introduced in bitcoin#17270 which added
  ```
  //! Necessary on some platforms
  extern char** environ;
  ```
  This should (finally) make the gitian build pass again (fix issue bitcoin#17525.).

  Built on top of bitcoin#17538 which should be merged first.

Top commit has no ACKs.

Tree-SHA512: 5c2054d52d0957aec3dc945b76d8e219187d22dc03889e7a88fb76049bf8e4a3e9f4da00dd1e9dd0351211f8e70d1a1b8ad7244f0348dab698e9d14b9d0c0bd4

contrib/devtools/symbol-check.py

@@ -48,7 +48,8 @@
 # Ignore symbols that are exported as part of every executable
 # // SYSCOIN
 IGNORE_EXPORTS = {
-'_edata', '_end', '__end__', '_init', '__bss_start', '__bss_start__', '_bss_end__', '__bss_end__', '_fini', '_IO_stdin_used', 'stdin', 'stdout', 'stderr', 'environ', '_environ', '__environ'
+'_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')