feat(ulp): build legacy ULP APIs through CMake v2 shim

components/esp_hal_uart/CMakeLists.txt

@@ -8,6 +8,22 @@ if(EXISTS "${CMAKE_CURRENT_LIST_DIR}/${target}/include")
     list(APPEND includes "${target}/include")
 endif()
 
+# TODO(IDF-15990): potentially remove __ULP_BUILD handling from esp_hal_uart
+if(__ULP_BUILD)
+    # LP-core UART and print code includes UART HAL headers from
+    # ulp/lp_core/lp_core/lp_core_uart.c and
+    # ulp/lp_core/lp_core/lp_core_print.c.
+    set(ulp_srcs)
+    if(ULP_TYPE STREQUAL "lp_core" AND CONFIG_SOC_UART_SUPPORTED)
+        list(APPEND ulp_srcs "uart_hal.c" "uart_hal_iram.c")
+    endif()
+
+    idf_component_register(SRCS ${ulp_srcs}
+                           INCLUDE_DIRS ${includes}
+                           REQUIRES esp_common soc hal)
+    return()
+endif()
+
 if(CONFIG_SOC_UART_SUPPORTED)
     list(APPEND srcs "uart_hal.c" "uart_hal_iram.c" "${target}/uart_periph.c")
 endif()