Merge #20594: Fix getauxval calls in randomenv.cpp

836a3dc02c Avoid weak-linked getauxval support on non-linux platforms (like macOS) (Jonas Schnelli)
41a413b317 Define correct symbols for getauxval (Jonas Schnelli)

Pull request description:

  PR #20358 made use of the two preprocessor symbols `HAVE_STRONG_GETAUXVAL` as well as `HAVE_WEAK_GETAUXVAL`.

  These symbols have not been defined in configure.ac. They where only passed selective as CRC32 CPPFLAGS in https://github.com/bitcoin/bitcoin/blob/master/src/Makefile.crc32c.include#L16.

  PR #20358 would have broken the macOS build since `getauxval` is not supported on macOS (but weak-linking does pass).

  This PR defines the two symbols correctly and reduces calls to `getauxval` to linux.

ACKs for top commit:
  laanwj:
    Code review ACK 836a3dc02c
  jonatack:
    utACK 836a3dc02c

Tree-SHA512: 6527f4a617b937f4c368a3cb1c162f1ac38a6f5e6341295554961eaf322906e9b27398a6f7b00819854ceebb5c828d3e6ce0a779edd769adc4053ce8beda3739

configure.ac

@@ -1116,18 +1116,20 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
   ]], [[
     getauxval(AT_HWCAP);
   ]])],
- [ AC_MSG_RESULT(yes); HAVE_STRONG_GETAUXVAL=1 ],
+ [ AC_MSG_RESULT(yes); HAVE_STRONG_GETAUXVAL=1; AC_DEFINE(HAVE_STRONG_GETAUXVAL, 1, [Define this symbol to build code that uses getauxval)]) ],
  [ AC_MSG_RESULT(no); HAVE_STRONG_GETAUXVAL=0 ]
 )
 
 AC_MSG_CHECKING(for weak getauxval support in the compiler)
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+    #ifdef __linux__
     unsigned long getauxval(unsigned long type) __attribute__((weak));
     #define AT_HWCAP 16
+    #endif
   ]], [[
     getauxval(AT_HWCAP);
   ]])],
- [ AC_MSG_RESULT(yes); HAVE_WEAK_GETAUXVAL=1 ],
+ [ AC_MSG_RESULT(yes); HAVE_WEAK_GETAUXVAL=1; AC_DEFINE(HAVE_WEAK_GETAUXVAL, 1, [Define this symbol to build code that uses getauxval (weak linking)]) ],
  [ AC_MSG_RESULT(no); HAVE_WEAK_GETAUXVAL=0 ]
 )