Fix a panic caused by the .synth() method when the VMOD is built with -O0.

This simply replaces the use of VRT_synth_strands() with
VRT_synth_blob(). That's more of a workaround than an explanation
of the problem.

Closes #2

src/vmod_file.c

@@ -604,8 +604,7 @@ vmod_reader_get(VRT_CTX, struct VPFX(file_reader) *rdr)
 VCL_VOID
 vmod_reader_synth(VRT_CTX, struct VPFX(file_reader) *rdr)
 {
-	const char *p[0];
-	struct strands strands = { 1, p };
+	VCL_BLOB blob;
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(rdr, FILE_READER_MAGIC);
@@ -622,8 +621,9 @@ vmod_reader_synth(VRT_CTX, struct VPFX(file_reader) *rdr)
 
 	AN(rdr->flags & RDR_MAPPED);
 	AN(rdr->addr);
-	strands.p[0] = rdr->addr;
-	VRT_synth_page(ctx, &strands);
+	blob = VRT_blob(ctx, "VMOD file blob()", rdr->addr, rdr->info->len - 1,
+			VMOD_FILE_BLOB_MAGIC);
+	VRT_synth_blob(ctx, blob);
 
 	AZ(pthread_rwlock_unlock(rdr->lock));
 	return;