[Bug other/67812] New: Default-PIE patch broke building compiler as PIE and on esp toolchains

["bugdal at aerifal dot cx" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67812

            Bug ID: 67812
           Summary: Default-PIE patch broke building compiler as PIE and
                    on esp toolchains
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bugdal at aerifal dot cx
  Target Milestone: ---

The default-pie patch added the following to gcc/Makefile.in:

+# We don't want to compile the compilers with -fPIE, it make PCH fail.
+COMPILER += @NO_PIE_CFLAGS@
+
+# Link with -no-pie since we compile the compiler with -fno-PIE.
+LINKER += @NO_PIE_FLAG@

This precludes building the compiler as PIE, which leads to multiple problems:

1. On existing PIE-by-default toolchains (ESP patches), -fno-PIE gets added to
NO_PIE_CFLAGS, but NO_PIE_FLAG remains blank, because the negative option was
called -nopie rather than -no-pie. Using -fno-PIE without -no-pie/-nopie
results in link errors on some host archs.

2. Refusal to build as PIE may violate distro policy of shipping only PIE
binaries.

3. For nommu systems, building as PIE is mandatory; non-PIE binaries simply
cannot run.

If there's an issue where PCH does not work with PIE then PCH should just be
disabled when the compiler is built as PIE. This worked fine before, and is
completely orthogonal to whether the compiler produces PIE by default; one is a
host issue and the other is a target issue.