bootstrap: try better workaround for builds on Linux/HPPA

The workaround currently present works fine without -O or with -O1, but fails
with -Os or -O2 and higher. Using -O2 is common e.g. in Gentoo, as resulting in
bugs like this:

https://bugs.gentoo.org/473276

Prevent the workaround for higher optimization levels to make bootstrapping
more likely to succeed.

This is still a workaround as ld still keeps crashing in some situations.

bootstrap

@@ -692,9 +692,12 @@ if ${cmake_system_linux}; then
   # avoid binutils problem with large binaries, e.g. when building CMake in debug mode
   # See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50230
   if ${cmake_machine_parisc}; then
+    # if -O[s23] is given the effect is inverted, so do not use the flag then
+    if [ "`echo "${CXXFLAGS}" | sed -r '/^(.* )?(-O[s234])( .*)?$/s/.*/-Os/'`" != "-Os" ]; then
       cmake_ld_flags="${LDFLAGS} -Wl,--unique=.text.*"
     fi
   fi
+fi
 
 #-----------------------------------------------------------------------------
 # Detect known toolchains on some platforms.