toolchain/59718: build.sh w/o -j broken since GCC 14 (tree-check.h)

[tnn%nygren.pp.se@localhost]

>Number:         59718
>Category:       toolchain
>Synopsis:       build.sh w/o -j broken since GCC 14 (tree-check.h)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Oct 21 11:55:00 +0000 2025
>Originator:     Tobias Nygren
>Release:        11.99.3
>Organization:
>Environment:
11.99.1 amd64
>Description:
Something is missing in the target dependency chain for GCC.
tree-check.h can be used before it has been generated.
This seems to not occur at -j2 or higher.
```
       link  backend/genattr
    compile  backend/genconditions.lo
       link  backend/genconditions
     create  backend/gencondmd.cc
    compile  backend/genpreds.lo
       link  backend/genpreds
     create  backend/tm-preds.h
     create  backend/tm_p.h
     create  backend/tm-constrs.h
    compile  backend/gencondmd.lo
In file included from /usr/src/external/gpl3/gcc/dist/gcc/recog.h:24,
                 from gencondmd.cc:40:
/usr/src/external/gpl3/gcc/dist/gcc/tree.h:519:10: fatal error: tree-check.h: No
 such file or directory
  519 | #include "tree-check.h"
```
>How-To-Repeat:
cd /usr/src
./build.sh -T ../tools -O ../obj -u -U -N 1 build

>Fix:
run build.sh with -j 2 or higher