Don't delete new dalvik-cache for otapreopt

otapreopt would incorrectly clear out the entire
/data/ota/$BOOT_SLOT/dalvik-cache/$ISA directory each time it compiled
an apk. This meant that pre-installed apks (from /system, /product,
etc) would have their compilation artifacts deleted during OTAs,
causing them to fallback to running from the APK or extracted dexs.

Bug: 181182967
Test: Manual OTA of blueline

Change-Id: I414424a8963e18e01b892a6e7ba2fb1beeb1a38d
diff --git a/cmds/installd/otapreopt.cpp b/cmds/installd/otapreopt.cpp
index cefcf64..ed31ad9 100644
--- a/cmds/installd/otapreopt.cpp
+++ b/cmds/installd/otapreopt.cpp
@@ -349,9 +349,6 @@
             }
         }
 
-        // Clear cached artifacts.
-        ClearDirectory(isa_path);
-
         // Check whether we have a boot image.
         // TODO: check that the files are correct wrt/ jars.
         std::string preopted_boot_art_path =
@@ -395,37 +392,6 @@
         return false;
     }
 
-    static void ClearDirectory(const std::string& dir) {
-        DIR* c_dir = opendir(dir.c_str());
-        if (c_dir == nullptr) {
-            PLOG(WARNING) << "Unable to open " << dir << " to delete it's contents";
-            return;
-        }
-
-        for (struct dirent* de = readdir(c_dir); de != nullptr; de = readdir(c_dir)) {
-            const char* name = de->d_name;
-            if (strcmp(name, ".") == 0 || strcmp(name, "..") == 0) {
-                continue;
-            }
-            // We only want to delete regular files and symbolic links.
-            std::string file = StringPrintf("%s/%s", dir.c_str(), name);
-            if (de->d_type != DT_REG && de->d_type != DT_LNK) {
-                LOG(WARNING) << "Unexpected file "
-                             << file
-                             << " of type "
-                             << std::hex
-                             << de->d_type
-                             << " encountered.";
-            } else {
-                // Try to unlink the file.
-                if (unlink(file.c_str()) != 0) {
-                    PLOG(ERROR) << "Unable to unlink " << file;
-                }
-            }
-        }
-        CHECK_EQ(0, closedir(c_dir)) << "Unable to close directory.";
-    }
-
     static const char* ParseNull(const char* arg) {
         return (strcmp(arg, "!") == 0) ? nullptr : arg;
     }