Configure script in release doesn't work on macOS Big Sur

[bmw]

If you build augeas on macOS 11 Big Sur there are linking problems. The error is the same as hercules-team/ruby-augeas#4 but I believe the cause is the configure script included in the release is not properly handling the macOS version number change from macOS 10.x to macOS 11 as described in threads like this one https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97865.

After building and installing Augeas from source on macOS 11, you can reproduce the problem running commands like:

python3 -m venv venv
. ./venv/bin/activate
pip install python-augeas
python break.py

where break.py is:

from augeas import Augeas
a = Augeas(flags=Augeas.NONE | Augeas.NO_MODL_AUTOLOAD)
a.set('/augeas/load/Httpd/lens', 'Httpd.lns')
a.load()
print(a.get('/augeas/load/Httpd/error'))

The output of this is:

/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/util.aug:115.2-123.51:Failed to compile comment_multiline
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/util.aug:116.20-.69:exception: Regular expression subtraction 'r1 - r2' failed
    r1: /[^ 	
].*[^ 	
]|[^ 	
]/
    r2: /.*\*/.*/

/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:78.26-.37:Could not load module Util for Util.indent
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:78.26-.37:Undefined variable Util.indent
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:168.4-.10:Undefined variable indent
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:177.13-.19:Undefined variable indent
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:182.21-.27:Undefined variable indent
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:187.18-.25:Undefined variable section
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:187.26-.44:Undefined variable directive
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:190.10-.18:Undefined variable content
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:204.13-.25:Undefined variable Util.stdexcl
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:206.20-.23:Undefined variable lns
/opt/homebrew/Cellar/augeas/1.12.0/share/augeas/lenses/dist/httpd.aug:206.24-.30:Undefined variable filter

This itself isn't a fatal error, although all of these errors parsing augeas lenses can cause significant problems later on.

I'm not 100% sure if this has been fixed by autoconf and friends, but I suspect it has and that this can be resolved by just building a new release with updated tools (which would also resolve #722).

[bmw]

Unfortunately the root problem here in libtool remains unresolved. See https://debbugs.gnu.org/cgi/bugreport.cgi?bug=44605.