Add a flag to logger

This commit adds one config flag in meson, to be used at build time.This
flag is to decide whether the logs will dump in a file or will go to the
console by default.

Test:
Image built with file logging enabled, and so all the logs are part of
log file.

$cat /var/lib/vpd/test.log |grep -i  "sanity"
FileName: /usr/src/debug/openpower-fru-vpd/1.0+git/vpd-manager/src/
logger.cpp, Line: 59 Performing sanity check for file path: /sys/bus/
spi/drivers/at25/spi12.0/eeprom

FileName: /usr/src/debug/openpower-fru-vpd/1.0+git/vpd-manager/src/
logger.cpp, Line: 59 Sanity checker Passed for /sys/bus/spi/drivers/
at25/spi12.0/eeprom

FileName: /usr/src/debug/openpower-fru-vpd/1.0+git/vpd-manager/src/
logger.cpp, Line: 59 Performing sanity check for file path: /sys/bus/
spi/drivers/at25/spi13.0/eeprom

FileName: /usr/src/debug/openpower-fru-vpd/1.0+git/vpd-manager/src/
logger.cpp, Line: 59 Sanity checker Passed for /sys/bus/spi/drivers/
at25/spi13.0/eeprom
~#

Change-Id: I3239683e643a06eeda6b0d23678c16bcf7cdf121
Signed-off-by: Alpana Kumari <alpankum@in.ibm.com>
diff --git a/vpd-manager/meson.build b/vpd-manager/meson.build
index a7f95c3..245e1d1 100644
--- a/vpd-manager/meson.build
+++ b/vpd-manager/meson.build
@@ -34,6 +34,7 @@
 parser_build_arguments = []
 if get_option('ibm_system').allowed()
     parser_build_arguments += ['-DIBM_SYSTEM']
+    parser_build_arguments += ['-DENABLE_FILE_LOGGING=true']
     vpd_manager_SOURCES += 'src/single_fab.cpp'
 endif