build: build with srcdir = builddir by default

srcdir != builddir is still possible, but this should help people who
are used to autotools feel more comfortable.

Signed-off-by: Evan Nemerson <evan@coeus-group.com>
Fix installation environment.

Signed-off-by: Evan Nemerson <evan@coeus-group.com>
plugins: add some missing newlines at EOF

Signed-off-by: Evan Nemerson <evan@coeus-group.com>
quicklz: build with QLZ_MEMORY_SAFE

Otherwise, QuickLZ can segfault when attempting to decompress malformed
data, which could result in a security vulnerability.

Signed-off-by: Evan Nemerson <evan@coeus-group.com>