lscpu: Use 4K buffer size instead of BUFSIZ

lscpu: Use 4K buffer size instead of BUFSIZ

Some lines in /proc/cpuinfo can be large e.g. flags and can then
truncate them in displaying them

BUFSIZ can vary quite a bit  e.g. glibc/linux systems its 8192
but on musl/linux and OSX its 1024, on mingW it is 256, some tests e.g.
x86_64-64cpu-linux6.2.tar.gz has added really long line for cpu flags
line which is greater than 1024 characters and hence this test fails
on musl because lscpu -s reports truncated string

Fixes x86_64-64cpu-linux6.2 tests

Signed-off-by: Khem Raj <raj.khem@gmail.com>
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