greenhills: fix the pow() function calculate error

Signed-off-by: guoshichao <guoshichao@xiaomi.com>

arch/arm/src/common/CMakeLists.txt

@@ -91,4 +91,8 @@ if(CONFIG_ARCH_HAVE_FETCHADD)
   list(APPEND SRCS ${ARCH_TOOLCHAIN_PATH}/arm_fetchadd.S)
 endif()
 
+if(CONFIG_ARCH_TOOLCHAIN_GHS)
+  list(APPEND SRCS ghs/lib_dummy.c)
+endif()
+
 target_sources(arch PRIVATE ${SRCS})

arch/arm/src/common/ghs/lib_dummy.c

@@ -46,6 +46,6 @@ void __gh_fputs_stdout(void)
 {
 }
 
-void exp2(void)
+void __gh_set_errno(int errno)
 {
 }