Exclude source/TegraExplorer from Makefile object list

The vendored tree under source/TegraExplorer is optional reference-only;
building it fails without extra usb/ headers. The payload uses bdk/ at repo
root instead.

Made-with: Cursor

Makefile

@@ -31,6 +31,9 @@ OBJS += $(patsubst $(BDKDIR)/%.S, $(BUILDDIR)/$(TARGET)/%.o, \
 		$(patsubst $(BDKDIR)/%.c, $(BUILDDIR)/$(TARGET)/%.o, \
 		$(call rwildcard, $(BDKDIR), *.S *.c)))
 
+# Optional vendored tree under source/TegraExplorer/ is not part of this payload build.
+OBJS := $(filter-out $(BUILDDIR)/$(TARGET)/TegraExplorer/%,$(OBJS))
+
 GFX_INC   := '"../$(SOURCEDIR)/gfx.h"'
 FFCFG_INC := '"../$(SOURCEDIR)/libs/fatfs/ffconf.h"'