build: Add -flto to CXXFLAGS
build: Add -flto to CXXFLAGS

Add -flto to CXXFLAGS to allow build optimization.

Change-Id: Icc7bd996bd512a0d84a35b6a0449f69611a69de1
Signed-off-by: Patrick Venture <36c53fa43f47f3fd67cb2fc38031827244d18a1f@google.com>

openbmc/phosphor-ipmi-blobs