Keep Windows .rsp files with Ninja

Ninja normally deletes each response .rsp file if the target build is successful. When debugging a program, we may need to see all the commands run before failure by keeping the .rsp files.

Ninja keeps the .rsp files after compilation by using option:

ninja -d keeprsp

Ninja is a build backend used by Meson build system and CMake as a fast, modern replacement for GNU Make. .rsp files are simply a plain text file containing the command fragment to be run on the command line.

For example, a build line:

cc -Iinc hello.c -lm

is implemented with an .rsp file by the build system as:

cc hello.rsp

where file foo.rsp contains

-Iinc hello.c -lm

There is currently not a Meson or CMake option to keep the .rsp files. Instead, manually invoke Ninja as above when Meson or CMake has configured the build. That is, instead of:

cmake --build build --target hello -v

or

meson compile -C build

do:

ninja -C build -d keeprsp hello