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

components/esp_hal_touch_sens/CMakeLists.txt

@@ -12,6 +12,16 @@ endif()
 # "include" should be behind "${target}/include", because `include_next` has sequence requirement
 list(APPEND includes "include")
 
+# TODO(IDF-15989): potentially remove __ULP_BUILD handling from esp_hal_touch_sens
+if(__ULP_BUILD)
+    # ULP touch support includes touch sensor HAL headers from
+    # ulp/ulp_riscv/ulp_core/ulp_riscv_touch.c and
+    # ulp/lp_core/lp_core/lp_core_touch.c.
+    idf_component_register(INCLUDE_DIRS ${includes}
+                           REQUIRES soc)
+    return()
+endif()
+
 # Touch Sensor related source files
 if(CONFIG_SOC_TOUCH_SENSOR_SUPPORTED)
     # Source files for the legacy touch hal driver