lcov: Disable the XS extension

lcov 2.6 makes "make install" depend on a new xs_lib target which runs
"perl Makefile.PL" with the host perl. That loads lcovutil.pm, so
do_install fails on hosts without Capture::Tiny:

  Can't locate Capture/Tiny.pm in @INC
  make: *** [Makefile:169: xs_lib] Error 2

The extension can't be cross-built this way, since it would use the host
perl configuration. It is an optional speedup and lcovutil.pm falls back
to pure Perl without it, so set LCOV_NO_XS=1.

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

meta-oe/recipes-support/lcov/lcov_2.6.bb

@@ -68,7 +68,7 @@ do_install() {
     # Makefile bakes the runtime --bindir/--libdir ($(PREFIX)/...) into the
     # installed perl modules and manpages, so folding ${D} into PREFIX would
     # embed the build path and trip the buildpaths QA check.
-    oe_runmake install PREFIX=${prefix} DESTDIR=${D} CFG_DIR=${sysconfdir} LCOV_PERL_PATH="/usr/bin/env perl"
+    oe_runmake install PREFIX=${prefix} DESTDIR=${D} CFG_DIR=${sysconfdir} LCOV_PERL_PATH="/usr/bin/env perl" LCOV_NO_XS=1
 
     # The upstream test suite is shipped under ${datadir}/lcov/tests and is
     # not needed at runtime. Its shell scripts pull in unwanted file-rdeps on