compiler: Rename host_build() to tools_build()

With the new TOOLS_LIBCRYPTO and some other changes, it seems that we are
heading towards calling this a tools build rather than a host build,
although of course it does happen on the host.

I cannot think of anything built by the host which cannot be described as
a tool, so rename this function.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

include/compiler.h

@@ -155,11 +155,12 @@ typedef unsigned long int uintptr_t;
 #endif
 
 /**
- * host_build() - check if we are building for the host
+ * tools_build() - check if we are building host tools
  *
  * @return true if building for the host, false if for a target
  */
-static inline bool host_build(void) {
+static inline bool tools_build(void)
+{
 #ifdef USE_HOSTCC
 	return true;
 #else