Description: pass -std=c++17 in CXXFLAGS
 Fixes build with libre2-dev 20240501 which requires at least c++-14
 Cherry-picked from the upstream commit which is for Firebird 5
Forwarded: https://github.com/FirebirdSQL/firebird/commit/936e045d50f4f6632017e1cb0edea6ef960fc80c
Bug-Debian: https://bugs.debian.org/1071759
Origin: upstream, https://github.com/FirebirdSQL/firebird/commit/936e045d50f4f6632017e1cb0edea6ef960fc80c

--- a/builds/posix/make.defaults
+++ b/builds/posix/make.defaults
@@ -104,7 +104,7 @@ GLOB_OPTIONS:=
 #____________________________________________________________________________
 
 # Global c++ flags: firebird needs no RTTI, choose build standard, make it build with icu-76.1
-PLUSPLUS_FLAGS:= -fno-rtti -std=c++11 -DU_SHOW_CPLUSPLUS_API=0 -DU_SHOW_CPLUSPLUS_HEADER_API=0
+PLUSPLUS_FLAGS:= -fno-rtti -std=c++17 -DU_SHOW_CPLUSPLUS_API=0 -DU_SHOW_CPLUSPLUS_HEADER_API=0
 
 # If this is defined then we use special rules useful for developers only
 IsDeveloper = @DEVEL_FLG@
--- a/configure.ac
+++ b/configure.ac
@@ -940,7 +940,7 @@ dnl if 64-bit mode, then archive tool, a
 fi
 
 XE_SAVE_ENV()
-CXXFLAGS="$CXXFLAGS -std=c++11"
+CXXFLAGS="$CXXFLAGS -std=c++17"
 AC_CACHE_CHECK([whether the C++ compiler understands noexcept], [ac_cv_cxx_noexcept], [
     AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[int f(int x) noexcept { return x + 1; }]], [[]])],
 	[ac_cv_cxx_noexcept=yes], [ac_cv_cxx_noexcept=no])])