tools: Add essential math.h for wasm build

If the experimental feature Wasm build enabled with multi thread
compiling, the COPYFILE (cp) maybe raise the error below:
```
cp: cannot create regular file 'math.h': file exists
```

This error cause by that the wasi-sdk don't provide the math.h for
non-wasi envrioment, for this case, provide a math.h for it instead of copy
file each time is better.

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

Author: no1wudi

include/wasm/.gitignore

@@ -0,0 +1,32 @@
+/****************************************************************************
+ * apps/include/wasm/math.h
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_WASM_MATH_H
+#define __INCLUDE_WASM_MATH_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+/* Forwards math.h to nuttx/include/nuttx/lib/math.h */
+
+#include <nuttx/lib/math.h>
+
+#endif /* __INCLUDE_WASM_MATH_H */

include/wasm/math.h

@@ -75,20 +75,12 @@ WAMR_MODE ?= INT
 WSRCS := $(MAINSRC) $(CSRCS)
 WOBJS := $(WSRCS:=$(SUFFIX).wo)
 
-# Copy math.h from $(TOPDIR)/include/nuttx/lib/math.h to $(APPDIR)/include/wasm/math.h
-# Using declaration of math.h is OK for Wasm build
-
-$(APPDIR)$(DELIM)include$(DELIM)wasm$(DELIM)math.h:
-ifeq ($(CONFIG_LIBM),)
-	$(call COPYFILE,$(TOPDIR)$(DELIM)include$(DELIM)nuttx$(DELIM)lib$(DELIM)math.h,$@)
-endif
-
 all:: $(WBIN)
 
 $(BINDIR)/wasm:
 	$(Q) mkdir -p $(BINDIR)/wasm
 
-depend:: $(APPDIR)$(DELIM)include$(DELIM)wasm$(DELIM)math.h $(BINDIR)/wasm
+depend:: $(BINDIR)/wasm
 
 $(WOBJS): %.c$(SUFFIX).wo : %.c
 	$(Q) $(WCC) $(WCFLAGS) -c $^ -o $@
@@ -108,7 +100,6 @@ $(WBIN): $(WOBJS)
 clean::
 	$(call DELFILE, $(WOBJS))
 	$(call DELFILE, $(WBIN))
-	$(call DELFILE, $(APPDIR)$(DELIM)include$(DELIM)wasm$(DELIM)math.h)
 
 endif # WASM_BUILD