[realtek-ambz] Fix float abi linking errors

builder/frameworks/realtek-ambz-sdk.py

@@ -238,7 +238,8 @@ env.Append(
         "_wps",
         "_p2p",
         "_dct",
-        "_rtlstd",
+        # use lib_rtlstd.a without some __aeabi functions
+        "_rtlstd_patch",
         "m",
         "c",
         "nosys",

builder/utils.py

@@ -49,6 +49,7 @@ def env_add_defaults(env, family_name: str, sdk_name: str):
         ],
         LIBPATH=[
             "$LD_DIR",
+            "$FIXUPS_DIR",
         ],
         CPPDEFINES=[
             ("LIBRETUYA", "1"),

platform/realtek-ambz/fixups/lib_rtlstd_patch.md

@@ -0,0 +1,14 @@
+# lib_rtlstd_patch.a
+
+```
+arm-none-eabi-gcc-ar xo lib_rtlstd.a
+arm-none-eabi-objcopy -N __aeabi_fsub rtl_eabi_cast_ram.o
+arm-none-eabi-objcopy -N __aeabi_fadd rtl_eabi_cast_ram.o
+arm-none-eabi-objcopy -N __aeabi_ui2f rtl_eabi_cast_ram.o
+arm-none-eabi-objcopy -N __aeabi_i2f rtl_eabi_cast_ram.o
+arm-none-eabi-objcopy --strip-debug --strip-unneeded ram_libc.o
+arm-none-eabi-objcopy --strip-debug --strip-unneeded ram_libgloss_retarget.o
+arm-none-eabi-objcopy --strip-debug --strip-unneeded rtl_eabi_cast_ram.o
+arm-none-eabi-objcopy --strip-debug --strip-unneeded rtl_math_ram.o
+arm-none-eabi-gcc-ar qs lib_rtlstd_patch.a *.o
+```