chore, make sure ac_c_werror_flag is off when hitting the libtool checks

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, move -ipo* flags to special_optiflags and provide via EXTRA_CFLAGS

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, add EXTRA_CFLAGS for all echse files to AM_CFLAGS

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'bld/dist' into next

* bld/dist:
  chore, add EXTRA_CFLAGS for all echse files to AM_CFLAGS
  chore, move -ipo* flags to special_optiflags and provide via EXTRA_CFLAGS
  chore, make sure ac_c_werror_flag is off when hitting the libtool checks