maintMakefile MAKE_CFLAGS: Does the `-C` option do anything?

In commit `1dfd55ca`, the added comment in `maintMakefile` reads:

> # Also force comments to be preserved.  This helps when using ccache, in
> # combination with GCC 7's implicit-fallthrough warning.

I am curious how this helps ccache. I tried running GCC with and without
the flags and it seems to have no effect.
You can try it for yourself with this script:

 #!/usr/bin/env bash

set -ux

cd $(mktemp -d)

cat > main.c <<EOF
#include <stdio.h>

// This is a comment!

int main()
{
  puts("Hello, the wonderful people in the bug-make mailing list!\n");
  return 0;
}
EOF

echo "GCC version: $(gcc --version)"

MAINT_MAKEFILE_OPTS='-Wall -Wextra -Werror -Wwrite-strings -Wshadow
-Wdeclaration-after-statement -Wbad-function-cast -Wformat-security
-Wtype-limits -Wunused-but-set-parameter -Wlogical-op -Wpointer-arith
-Wignored-qualifiers -Wformat-signedness -Wduplicated-cond -g -O2 -c'
MY_OPTS='-gno-record-gcc-switches'

gcc $MAINT_MAKEFILE_OPTS $MY_OPTS -o main1.o main.c
gcc $MAINT_MAKEFILE_OPTS $MY_OPTS -C -o main2.o main.c

diff --report-identical-files main1.o main2.o

You should see the resulting files are identical.


The reason I ask is because I am using the `clangd` language server in
neovim (using the `bear` tool to generate a `compile_commands.json` file)
and it works great expect that I always get this error: `Invalid argument
'-C' only allowed with '-E'`. I am thinking that `gcc` just silently
ignores the `-C` switch when `-E` is not also specified, unless I'm missing
something. If I am correct, can we remove the `-C` flag from
`maintMakefile`?