flang build error on Linux25.04 ; cmake3.31.6 ; gcc14.2.0

[NicolasAnquetil]

I tryed to build flang on stock Ubuntu 25.04 ; cmake 3.31.6 ; gcc 14.2.0 ; fresh clone of llvm-project (as of 11/18/2025)
.
I followed the instructions in https://flang.llvm.org/docs/GettingStarted.html , for "in tree" build.
The only change is anadded an option to limit jobs creation by ninja : -DFLANG_PARALLEL_COMPILE_JOBS=4 to avoid freezing my machine.

Ninja compiled many of the files, but stops on "Building CXX object tools/flan...les/FortranLower.dir/ConvertExpr.cpp.o"

I am attaching the log file for the error only
error.log

Following discussion on Discord, I could finally build by changing -DFLANG_ENABLE_WERROR=ON (from https://flang.llvm.org/docs/GettingStarted.html) to OFF
(Notice that the buildbot is using that same -DFLANG_ENABLE_WERROR=OFF option)

So it is an issue that can be stepped over, but the solution is a bit radical