Remove copy & paste cruft from the mips64 combo.

libthread_db hasn't been in bionic for years.

Change-Id: Ibc036d894c6b6bf9ee4653f95ff7a000a223cb2e
diff --git a/core/combo/TARGET_linux-mips64.mk b/core/combo/TARGET_linux-mips64.mk
index f01cdd1..f8bda10 100644
--- a/core/combo/TARGET_linux-mips64.mk
+++ b/core/combo/TARGET_linux-mips64.mk
@@ -137,7 +137,6 @@
 
 libc_root := bionic/libc
 libm_root := bionic/libm
-libthread_db_root := bionic/libthread_db
 
 
 ## on some hosts, the target cross-compiler is not available so do not run this command
@@ -168,7 +167,7 @@
 	$(KERNEL_HEADERS) \
 	$(libm_root)/include \
 	$(libm_root)/include/mips \
-	$(libthread_db_root)/include
+
 # TODO: perhaps use $(libm_root)/include/mips64 instead of mips ?
 
 TARGET_CRTBEGIN_STATIC_O := $(TARGET_OUT_INTERMEDIATE_LIBRARIES)/crtbegin_static.o