pixi: bound the parallel build on Linux (#1252)

cmake --build --parallel without a number makes the Makefile generator run
an unbounded make -j, which exhausts the memory of the GitHub runners: the
ubuntu pixi job dies with 'The runner has received a shutdown signal' and
no compiler error. Override the build task on linux-64 to use $(nproc);
the Visual Studio generator on Windows is already bounded to the cores.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: facontidavide

pixi.toml

@@ -11,6 +11,9 @@ test = "PATH=\"$PATH;$PIXI_PROJECT_ROOT/build/Release\" ctest --test-dir build -
 
 [target.linux-64.tasks]
 test = "./build/tests/behaviortree_cpp_test"
+# With Makefiles, --parallel without a number runs an unbounded make -j that
+# exhausts the memory of the CI runners; bound it to the number of cores.
+build = "mkdir -p build && cd build && cmake ../ -DCMAKE_BUILD_TYPE=Release && cmake --build . --parallel $(nproc) --config Release"
 
 [tasks]
 build = "mkdir -p build && cd build && cmake ../ -DCMAKE_BUILD_TYPE=Release && cmake --build . --parallel --config Release"