arrow

GH-38902: [R] Handle failing library detection with pkg-config (#38970)

### Rationale for this change

We can get into a broken state with a working test compile in `nixlibs.R` but empty `PKG_LIBS` when pkg-config fails to find some libraries (e.g. libcurl on mac due to missing system stubs) in `configure`. This leads to a failed test compile in configure with pc errors silenced.

### What changes are included in this PR?

Catch this and rerun the pkg-config-less library detection that should fix this in most cases.

### Are these changes tested?

locally and on cran (where this error first surfaced)
* Closes: #38902

Lead-authored-by: Jacob Wujciak-Jens <jacob@wujciak.de>
Co-authored-by: Jonathan Keane <jkeane@gmail.com>
Signed-off-by: Jacob Wujciak-Jens <jacob@wujciak.de>