rp2/CMakeLists.txt: Set the appropriate mpy-cross flags on all targets.

This commit lets the RP2 port build system use the appropriate flags to
pass to "mpy-cross" when building frozen MPY files as part of the build
process.

Now all possible variants (RP2040, RP2350/Arm, and RP2350/RV32) have
their right flags assigned, falling back the flags set of the RP2040 if
a new variant is introduced.  Before these changes all variants would
use the RP2040 set of flags which may be a bit of an issue when building
code for the RP2350 in RV32 mode.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

Author: agatti

ports/rp2/CMakeLists.txt

@@ -487,7 +487,16 @@ list(APPEND MICROPY_SOURCE_QSTR
 )
 
 # Define mpy-cross flags
-set(MICROPY_CROSS_FLAGS -march=armv6m)
+if (${PICO_PLATFORM} STREQUAL "rp2040")
+    set(MICROPY_CROSS_FLAGS "-march=armv6m")
+elseif (${PICO_PLATFORM} STREQUAL "rp2350-arm-s")
+    set(MICROPY_CROSS_FLAGS "-march=armv7m")
+elseif (${PICO_PLATFORM} STREQUAL "rp2350-riscv")
+    set(MICROPY_CROSS_FLAGS "-march=rv32imc -march-flags=zba,zcmp")
+else()
+    message(WARNING "Unknown PICO_PLATFORM version (${PICO_PLATFORM}), falling back to rp2040")
+    set(MICROPY_CROSS_FLAGS "-march=armv6m")
+endif()
 
 # Set the frozen manifest file
 if (MICROPY_USER_FROZEN_MANIFEST)