pico-serprog: enable building for multiple pico chips

rp2040 and rp2530 platforms can't share a cmake build directory. we
could just delete the build directory after every compilation, but that
would be really wasteful (every tool would need to be recomiled every
time. instead create new build directories as new plaforms are found
and symlink them to the point where the build directory used to be.

to find out which platform we're compiling for, we crudely parse the
board headers file.

there surely would be better ways to do this, but this hack works
with all the boards in pico-sdk 2.1.0.

Signed-off-by: Riku Viitanen <riku.viitanen@protonmail.com>

include/rom.sh

@@ -11,7 +11,14 @@ mkserprog()
 	basename -as .h "$serdir/"*.h > "$TMPDIR/ser" || $err "!mk $1 $TMPDIR"
 
 	while read -r sertarget; do
-		[ "$1" = "rp2040" ] && x_ cmake -DPICO_BOARD="$sertarget" \
+		[ "$1" = "rp2040" ] &&
+		    x_ rm -rf "$sersrc/build" \
+		    && (pt=$(x_ grep "pico_cmake_set" \
+		          "$picosdk/src/boards/include/boards/$sertarget.h" \
+		        | grep "PICO_PLATFORM" | cut -d= -f2 | tr -d [:blank:])
+		        mkdir -p "$sersrc/build_$pt"
+			ln -srf "$sersrc/build_$pt/" "$sersrc/build") \
+		    && x_ cmake -DPICO_BOARD="$sertarget" \
 		    -DPICO_SDK_PATH="$picosdk" -B "$sersrc/build" "$sersrc" \
 		    && x_ cmake --build "$sersrc/build"
 		[ "$1" = "stm32" ] && x_ make -C "$sersrc" \