D379: 863_0001-configure.ac-restore-user-CFLAGS-before-checking-fun.patch

Update patch to cover libraries search (e.g. iconv).

D378: 864_0001-configure.ac-restore-user-CFLAGS-before-checking-fun.patch

Please describe the bug and your patch here. A long title is not a sufficient
description. tia.

@werner, have you looked into the patch?

AC_CHECK_FUNCS([mmap]) on Fedora fails to find mmap() due to missing -fPIC.
/usr/bin/ld: /tmp/ccvNyAcN.o: relocation R_X86_64_PC32 against undefined symbol
`mmap@@GLIBC_2.2.5' can not be used when making a shared object; recompile with
-fPIC

We have -fPIC somewhere in default CFLAGS, so just resotre user CFLAGS
before making checks for functions.

That seems to be a regression due to commit 02eb9fc9d5863abcfed6af704e618f8cac7cc2e8

    If the user's CFLAGS include -Werror, then some configure tests fail.
    To avoid this, we only add the user's CFLAGS after all of the
    configure tests have run.

That patch was obviously wrong because configure now has a different picture on
the build system than make. A better solution to the -Werrror problem would be
to pass -Werror only to the make invocation - or more robust to add an
--enable-werror configure flag.

Fixed in 4b57359ef3ce0b87e15889e12ef0fcd23f62dcb4.

Reverted 4b57359ef3ce0b87e15889e12ef0fcd23f62dcb4.

Note that simply reverting 02eb9fc9d5863abcfed6af704e618f8cac7cc2e8 will make
our sanitizer build miscompile, likely because -fsanitize=x breaks some test.
This would be easy to fix with my approach, but Werner does not like it.

Justus, I mentioned several solutions on Jabber which do not affect the rule not
to modify CFLAGS.

I can't remember either. We should swicth back to mailing lists for such things.

One obvious thing is to figure the test which bails on -Werror and fix that test.