sbang.py: use os.uname and branch on kernel version

[haampie]

Remove Linux headers as a dependency of Spack.

The value has changed exactly only once in git history, and seems non-configurable.

[tgamblin]

Why risk IndexError when you don't have to?

Suggested change

	major, minor = (int(x) for x in release.split(".")[:2])
	system_shebang_limit = 255 if (major, minor) >= (5, 1) else 127
	version_tuple = tuple(int(x) for x in release.split("."))
	system_shebang_limit = 255 if version_tuple >= (5, 1) else 127

[haampie]

Slicing doesn't have that issue:

>>> [][:2]
[]

[tgamblin]

@finkandreas @tvoskui @AndresYague @jonasjucker does this still work for you? This is a simpler approach than #43290 and will work regardless of whether kernel headers are installed.

[tvoskui]

@finkandreas @tvoskui @AndresYague @jonasjucker does this still work for you? This is a simpler approach than #43290 and will work regardless of whether kernel headers are installed.

I just tried this out and I get inconsistent results. 4.18 would put it at the lower limit, but the header is at 256

>>> import os
>>> os.uname().release
'4.18.0-553.115.1.el8_10.x86_64'

$ cat /usr/include/linux/binfmts.h | grep BINPRM_BUF_SIZE 
#define BINPRM_BUF_SIZE 256

Also, the proposed code fails on that release string too

>>> release = os.uname().release
>>> version_tuple = tuple(int(x) for x in release.split("."))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in <genexpr>
ValueError: invalid literal for int() with base 10: '0-553'