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>
diff --git a/common/image.c b/common/image.c
index 2f2fd05..66685b4 100644
--- a/common/image.c
+++ b/common/image.c
@@ -460,11 +460,11 @@
 			ret = -ENOSPC;
 		break;
 	case IH_COMP_GZIP:
-		if (!host_build() && CONFIG_IS_ENABLED(GZIP))
+		if (!tools_build() && CONFIG_IS_ENABLED(GZIP))
 			ret = gunzip(load_buf, unc_len, image_buf, &image_len);
 		break;
 	case IH_COMP_BZIP2:
-		if (!host_build() && CONFIG_IS_ENABLED(BZIP2)) {
+		if (!tools_build() && CONFIG_IS_ENABLED(BZIP2)) {
 			uint size = unc_len;
 
 			/*
@@ -478,7 +478,7 @@
 		}
 		break;
 	case IH_COMP_LZMA:
-		if (!host_build() && CONFIG_IS_ENABLED(LZMA)) {
+		if (!tools_build() && CONFIG_IS_ENABLED(LZMA)) {
 			SizeT lzma_len = unc_len;
 
 			ret = lzmaBuffToBuffDecompress(load_buf, &lzma_len,
@@ -487,7 +487,7 @@
 		}
 		break;
 	case IH_COMP_LZO:
-		if (!host_build() && CONFIG_IS_ENABLED(LZO)) {
+		if (!tools_build() && CONFIG_IS_ENABLED(LZO)) {
 			size_t size = unc_len;
 
 			ret = lzop_decompress(image_buf, image_len, load_buf, &size);
@@ -495,7 +495,7 @@
 		}
 		break;
 	case IH_COMP_LZ4:
-		if (!host_build() && CONFIG_IS_ENABLED(LZ4)) {
+		if (!tools_build() && CONFIG_IS_ENABLED(LZ4)) {
 			size_t size = unc_len;
 
 			ret = ulz4fn(image_buf, image_len, load_buf, &size);
@@ -503,7 +503,7 @@
 		}
 		break;
 	case IH_COMP_ZSTD:
-		if (!host_build() && CONFIG_IS_ENABLED(ZSTD)) {
+		if (!tools_build() && CONFIG_IS_ENABLED(ZSTD)) {
 			struct abuf in, out;
 
 			abuf_init_set(&in, image_buf, image_len);