build: Add meson build for phosphor-host-ipmi

Create meson and meson_options for the existing features.

Removed sample.h/cpp since that is not used at all.

Tested:
Ipmi command works fine the cleanup.
```
$ systemctl status phosphor-ipmi-host
● phosphor-ipmi-host.service - Phosphor Inband IPMI
     Loaded: loaded (/lib/systemd/system/phosphor-ipmi-host.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 1970-01-08 21:20:56 UTC; 21s ago
   Main PID: 24987 (ipmid)
     CGroup: /system.slice/phosphor-ipmi-host.service
             └─24987 /tmp/ipmid

Jan 08 21:20:56 $HOST ipmid[24987]: Registering OEM:[0X002B79], Cmd:[0X30] for Ethstats Commands
Jan 08 21:20:56 $HOST ipmid[24987]: Registering OEM:[0X00C2CF], Cmd:[0X30] for Ethstats Commands
Jan 08 21:20:56 $HOST ipmid[24987]: Registering OEM:[0X002B79], Cmd:[0X32] for Sys Commands
Jan 08 21:20:56 $HOST ipmid[24987]: Registering OEM:[0X002B79], Cmd:[0X02] for I2C
Jan 08 21:20:56 $HOST ipmid[24987]: Registering OEM:[0X00C2CF], Cmd:[0X02] for I2C
Jan 08 21:20:56 $HOST ipmid[24987]: I2C_WHITELIST_CHECK is disabled, do not populate whitelist
Jan 08 21:20:56 $HOST ipmid[24987]: Registering OEM:[0X00C2CF], Cmd:[0X04] for Manual Zone Control
Jan 08 21:20:56 $HOST systemd[1]: Started Phosphor Inband IPMI.
Jan 08 21:20:56 $HOST ipmid[24987]: Loading whitelist filter
Jan 08 21:20:56 $HOST ipmid[24987]: Set restrictedMode = true
(reverse-i-search)`ipmi': systemctl status phosphor-^Cmi-host

$ ipmitool mc info
Device ID                 : 32
Device Revision           : 1
Firmware Revision         : 0.00
IPMI Version              : 2.0
Manufacturer ID           : 7244
Manufacturer Name         : Quanta Computer Inc.
Product ID                : 14426 (0x385a)
Product Name              : Unknown (0x385A)
Device Available          : yes
Provides Device SDRs      : yes
Additional Device Support :
    Sensor Device
    SEL Device
    FRU Inventory Device
    Chassis Device
Aux Firmware Rev Info     :
    0x00
    0x00
    0x00
    0x00
```

Change-Id: Ibaea9eea802b063a0207320654cbb817fde30c2a
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/app/meson.build b/app/meson.build
new file mode 100644
index 0000000..5e89b27
--- /dev/null
+++ b/app/meson.build
@@ -0,0 +1,15 @@
+app_inc = include_directories('.')
+
+app_pre = declare_dependency(include_directories: [root_inc, app_inc])
+
+app_lib = static_library(
+  'app',
+  'channel.cpp',
+  'watchdog.cpp',
+  'watchdog_service.cpp',
+  implicit_include_directories: false,
+  dependencies: app_pre)
+
+app_dep = declare_dependency(
+  link_with: app_lib,
+  dependencies: app_pre)