gh-115765: Don't use deprecated AC_EGREP_* macros in configure.ac

[erlend-aasland]

See Autoconf docs:

• https://www.gnu.org/software/autoconf/manual/autoconf-2.72/html_node/Running-the-Preprocessor.html#index-AC_005fEGREP_005fHEADER-1

• Issue: Upgrade to GNU Autoconf 2.72 #115765

[erlend-aasland]

@mhsmith, would you like to review this?

[erlend-aasland]

@corona10, feel free to take a look at this, if you have the time.

[erlend-aasland]

@mhsmith, thanks for the review; I addressed your remarks in 9c3596d. PTAL.

[erlend-aasland]

Found the culprit; typo on my end! ✅

[erlend-aasland]

Now, there's one more thing we should add before landing this: support configure cache.

[erlend-aasland]

Now, there's one more thing we should add before landing this: support configure cache.

I'm not sure we want to automatically generate the cache variable name in this macro. The first argument would need heavy string modifications to end up as a usable identifier. Perhaps it is best to introduce a new param for the cache variable name.

[mhsmith]

Alternatively, all but one usage of PY_CHECK_CPP could be replaced with AX_CHECK_DEFINE, which has caching already built in.

[erlend-aasland]

Alternatively, all but one usage of PY_CHECK_CPP could be replaced with AX_CHECK_DEFINE, which has caching already built in.

That's a good suggestion; I'll have a look in a day or two.

UPDATE: Created alternative PR gh-116016.

[erlend-aasland]

Alternatively, all but one usage of PY_CHECK_CPP could be replaced with AX_CHECK_DEFINE, which has caching already built in.

For the glibc check; do we really need to worry about glibc < 2.1?

[mhsmith]

I agree, so #116016 looks like the way to go.

[erlend-aasland]

Superseded by #116016