[Bug driver/111527] COLLECT_GCC_OPTIONS option hits single-variable limits too early

["deepadeepthi98 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111527

--- Comment #7 from Deepthi H <deepadeepthi98 at gmail dot com> ---
We've a solution for this issue.

When gcc/g++ is called using the @response-file.rsp syntax, gcc should forward
the argument to its subprocesses. Previously the files were expanded which
could lead to excessively long argument lists and 'cc1: execv: Argument list
too long' errors.

In particular, CMake and Ninja tend to create a lot of '-isystem' include
directories, requiring allowing the forwarding in spec files by using %@{i*}.

In xputenv method, If the ENV variable size greater then 128kb then we split
the ENV variable(i.e COLLECT_GCC_OPTIONS) where each chunk will be 128kb in
length.

GCC passes the entire command line, including expanded @rsp-files to the
collect2 in environment variable COLLECT_GCC_OPTIONS. This can exceed the build
environment's kernel's environment variable length limit. In this workaround,
environment variables longer than 128kb are split into multiple variables and
stitched back together in collect2.

The patch is attached here. 
And, the patch output of the example code given in 'Description' as below:

=======
sunild@BFT-LPT-I-051:~$ $GCC_PATH/gcc -c a.c -DA=$big_100k_var
-DB=$big_100k_var -v
Using built-in specs.
COLLECT_GCC=/home/sunild/GCC_Driver/bin/home/sunild/GCC_Driver/build/bin/gcc
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/sunild/GCC_Driver/build
--enable-languages=c --disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.1 20240426 (experimental) (GCC)
COLLECT_GCC_OPTIONS_0='-c' '-D'
'A=00000000000000000000000000000000000000000000000000000000
COLLECT_GCC_OPTIONS_1=000000000000000000000000000000000000000000000000000000000000000000000
COLLECT_GCC_OPTIONS_COUNT=2

=======

Let us know your comments on this solution. Such a solution is acceptable to
change the gcc driver?