Move install to separate module

Build libinstall as a shared library. Also drop the dependency on the
global variables in common.h.

Test: unit tests pass, sideload an OTA
Change-Id: I30a20047768ce00689fc0e7851c1c5d712a365a0
diff --git a/fsck_unshare_blocks.cpp b/fsck_unshare_blocks.cpp
index ce6940a..e74f8ba 100644
--- a/fsck_unshare_blocks.cpp
+++ b/fsck_unshare_blocks.cpp
@@ -36,7 +36,7 @@
 #include <android-base/unique_fd.h>
 #include <fstab/fstab.h>
 
-#include "roots.h"
+#include "otautil/roots.h"
 
 static constexpr const char* SYSTEM_E2FSCK_BIN = "/system/bin/e2fsck_static";
 static constexpr const char* TMP_E2FSCK_BIN = "/tmp/e2fsck.bin";