Fix clang-analyzer-core.uninitialized.Branch warnings

Bug: 154760495
Test: make with WITH_TIDY=1 and DEFAULT_GLOBAL_TIDY_CHECKS=clang-analyzer-core.uninitialized.Branch
Change-Id: I569749166177c25e63b32fb468dccd13797acc05
diff --git a/tools/bit/adb.cpp b/tools/bit/adb.cpp
index fa7d3d4..f521a63 100644
--- a/tools/bit/adb.cpp
+++ b/tools/bit/adb.cpp
@@ -200,7 +200,7 @@
 
 static int
 skip_unknown_field(int fd, uint64_t tag, char* scratch, int scratchSize) {
-    bool done;
+    bool done = false;
     int err;
     uint64_t size;
     switch (tag & 0x7) {