setup: relax -Werror for declaration-after-statement on Python 3.9
It turns out Python 3.9 introduces such declarations in the headers, eg
cpython/abstract.h:189:5: error: ISO C90 forbids mixed declarations and code [-Werror=declaration-after-statement]
so we have to be more relaxed when compiling for 3.9.
Differential Revision: https://phab.mercurial-scm.org/D8327
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false