binarystore: Create new shared library for binarystore

Move main.cpp to new shared library so blobtool don't include main.cpp.

Tested:

```
$ ninja install
[0/1] Installing files.
Installing src/libbinarystore.so to /usr/local/lib/blob-ipmid
Installing src/blobtool to /usr/local/bin

```

Change-Id: I16a4bb0be1dde833398ede330c56ac520ec39000
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/src/meson.build b/src/meson.build
index 7fec5ed..5432b3a 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -12,8 +12,7 @@
 )
 
 binarystoreblob_lib = library(
-  'binarystore',
-  'main.cpp',
+  'binarystoreblob',
   'binarystore.cpp',
   'sys.cpp',
   'sys_file_impl.cpp',
@@ -21,8 +20,6 @@
   src_pb,
   implicit_include_directories: false,
   dependencies: binarystoreblob_pre,
-  install: true,
-  install_dir: get_option('libdir') / 'blob-ipmid'
 )
 
 binarystoreblob_dep = declare_dependency(
@@ -30,6 +27,15 @@
   dependencies: binarystoreblob_pre
 )
 
+library(
+  'binarystore',
+  'main.cpp',
+  implicit_include_directories: false,
+  dependencies: binarystoreblob_dep,
+  install: true,
+  install_dir: get_option('libdir') / 'blob-ipmid'
+)
+
 if not get_option('blobtool').disabled()
   executable(
     'blobtool',