Merge bitcoin#24633: Bugfix: configure: Quote SUPPRESS_WARNINGS sufficiently to preserve brackets

5a157eb Bugfix: configure: Only avoid -isystem for exact /usr/include path (Luke Dashjr)
556ee6f Bugfix: configure: Quote SUPPRESS_WARNINGS sufficiently to preserve brackets (Luke Dashjr)

Pull request description:

  The regex includes `[/ ]` which is supposed to match either a forward slash or a space, but m4 treats the brackets as special characters and effectively strips them out, leading to -isystem /usr/include paths except for in the typical scenario where it is the final parameter in the flag string.

ACKs for top commit:
  hebasto:
    ACK 5a157eb, tested on Ubuntu 22.04 with clang 14.0.
  vasild:
    ACK 5a157eb

Tree-SHA512: 5c8c282b647b7853b8fad1b5b473703c4a0635073d2685a8ac984151046e2c6a859e6972465419d27356dd29a47f21a2a3a6ad402ec434fe1f9882e5a35f0749

Author: fanquake

configure.ac

@@ -1274,7 +1274,7 @@ dnl Do not change "-I/usr/include" to "-isystem /usr/include" because that
 dnl is not necessary (/usr/include is already a system directory) and because
 dnl it would break GCC's #include_next.
 AC_DEFUN([SUPPRESS_WARNINGS],
-         [$(echo $1 |${SED} -E -e 's/(^| )-I/\1-isystem /g' -e 's;-isystem /usr/include([/ ]|$);-I/usr/include\1;g')])
+         [[$(echo $1 |${SED} -E -e 's/(^| )-I/\1-isystem /g' -e 's;-isystem /usr/include/*( |$);-I/usr/include\1;g')]])
 
 dnl enable-fuzz should disable all other targets
 if test "$enable_fuzz" = "yes"; then