rp2: Add temporary workaround for GCC 15.1 build failure.

This is a workaround for this upstream issue:
https://github.com/raspberrypi/pico-sdk/issues/2448

Can be removed after the next pico-sdk update.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

ports/rp2/CMakeLists.txt

@@ -84,6 +84,9 @@ endif()
 list(APPEND GIT_SUBMODULES lib/mbedtls)
 list(APPEND GIT_SUBMODULES lib/tinyusb)
 
+# Workaround for pico-sdk host toolchain issue, see directory for details
+list(APPEND CMAKE_MODULE_PATH "${MICROPY_PORT_DIR}/tools_patch")
+
 # Include component cmake fragments
 include(${MICROPY_DIR}/py/py.cmake)
 include(${MICROPY_DIR}/extmod/extmod.cmake)

ports/rp2/tools_patch/Findpioasm.cmake

@@ -0,0 +1,58 @@
+# Finds (or builds) the pioasm executable
+#
+# This will define the following imported targets
+#
+#     pioasm
+#
+
+# This is a temporary patched copy of pico-sdk file Findpioasm.cmake to work around
+# a host toolchain issue with GCC 15.1:
+# https://github.com/raspberrypi/pico-sdk/issues/2448
+
+if (NOT TARGET pioasm)
+    # todo we would like to use pckgconfig to look for it first
+    # see https://pabloariasal.github.io/2018/02/19/its-time-to-do-cmake-right/
+
+    include(ExternalProject)
+
+    set(PIOASM_SOURCE_DIR ${PICO_SDK_PATH}/tools/pioasm)
+    set(PIOASM_BINARY_DIR ${CMAKE_BINARY_DIR}/pioasm)
+    set(PIOASM_INSTALL_DIR ${CMAKE_BINARY_DIR}/pioasm-install CACHE PATH "Directory where pioasm has been installed" FORCE)
+
+    set(pioasmBuild_TARGET pioasmBuild)
+    set(pioasm_TARGET pioasm)
+
+    if (NOT TARGET ${pioasmBuild_TARGET})
+        pico_message_debug("PIOASM will need to be built")
+#        message("Adding external project ${pioasmBuild_Target} in ${CMAKE_CURRENT_LIST_DIR}}")
+        ExternalProject_Add(${pioasmBuild_TARGET}
+                PREFIX pioasm
+                SOURCE_DIR ${PIOASM_SOURCE_DIR}
+                BINARY_DIR ${PIOASM_BINARY_DIR}
+                INSTALL_DIR ${PIOASM_INSTALL_DIR}
+                CMAKE_ARGS
+                    "--no-warn-unused-cli"
+                    "-DCMAKE_MAKE_PROGRAM:FILEPATH=${CMAKE_MAKE_PROGRAM}"
+                    "-DPIOASM_FLAT_INSTALL=1"
+                    "-DCMAKE_INSTALL_PREFIX=${PIOASM_INSTALL_DIR}"
+                    "-DCMAKE_RULE_MESSAGES=OFF" # quieten the build
+                    "-DCMAKE_INSTALL_MESSAGE=NEVER" # quieten the install
+                    # Toolchain workaround follows
+                    "-DCMAKE_CXX_FLAGS=-include cstdint"
+                CMAKE_CACHE_ARGS "-DPIOASM_EXTRA_SOURCE_FILES:STRING=${PIOASM_EXTRA_SOURCE_FILES}"
+                BUILD_ALWAYS 1 # force dependency checking
+                EXCLUDE_FROM_ALL TRUE
+                )
+    endif()
+
+    if (CMAKE_HOST_WIN32)
+        set(pioasm_EXECUTABLE ${PIOASM_INSTALL_DIR}/pioasm/pioasm.exe)
+    else()
+        set(pioasm_EXECUTABLE ${PIOASM_INSTALL_DIR}/pioasm/pioasm)
+    endif()
+    add_executable(${pioasm_TARGET} IMPORTED GLOBAL)
+    set_property(TARGET ${pioasm_TARGET} PROPERTY IMPORTED_LOCATION
+            ${pioasm_EXECUTABLE})
+
+    add_dependencies(${pioasm_TARGET} ${pioasmBuild_TARGET})
+endif()