Fix libunwind version check with patch releases

[nalimilan]

libunwind patch releases like 1.2.1 have UNW_VERSION_MINOR = 2.1, which
makes the comparison fail. Use a more robust comparison which excludes
all versions between 1.0 and 1.2 instead.
https://savannah.nongnu.org/bugs/index.php?52529

Fixes #23615, #24802.

[eli-schwartz]

$ cat /tmp/floating-math.h
#if (2.1 != 0 && 2.1 != 1)
#endif
$ cpp /tmp/floating-math.h 
# 1 "/tmp/floating-math.h"
# 1 "<built-in>"
# 1 "<command-line>"
# 31 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 32 "<command-line>" 2
# 1 "/tmp/floating-math.h"
/tmp/floating-math.h:1:6: error: floating constant in preprocessor expression
 #if (2.1 != 0 && 2.1 != 1)
      ^~~
/tmp/floating-math.h:1:18: error: floating constant in preprocessor expression
 #if (2.1 != 0 && 2.1 != 1)
                  ^~~

[nalimilan]

Damn, so even this isn't enough to fix the comparison issue... Then I don't know what we can do except for fixing libunwind upstream. :-(

[yuyichao]

It is fixed upstream...

[nalimilan]

Ah, good to know, that's indeed libunwind/libunwind#30. Too bad there hasn't been any release since then.