Show install path in "adb --version" and "fastboot --version".

Bug: http://b/36766455
Bug: http://b/34691048
Test: ran tests
Change-Id: I4b67ec54d41a281fe7a33c017d3cfbc8055e3b43
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 2927b16..a99ba23 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -1536,6 +1536,7 @@
                 setvbuf(stderr, nullptr, _IONBF, 0);
             } else if (strcmp("version", longopts[longindex].name) == 0) {
                 fprintf(stdout, "fastboot version %s\n", FASTBOOT_REVISION);
+                fprintf(stdout, "Installed as %s\n", android::base::GetExecutablePath().c_str());
                 return 0;
             } else if (strcmp("slot", longopts[longindex].name) == 0) {
                 slot_override = std::string(optarg);