Re-enable tests in %check

Upstream <https://git.libreoffice.org/core/+/
a58e086ededb8442938e81f971dfae36ef7eb076%5E!> "rework the default make target"
towards libreoffice-7-0 had dropped the unitcheck and slowcheck targets from the
default target.

But after the preceding b27571d688 "Enable LTO
again", that reveals that there appears to still be issues with LTO at least on
i686, which fails with

> ### unexpected exception content! failed
> ### unexpected exception content! failed
> ### unexpected exception content! failed
> exception test failed
> oneway exception test failed
> exception occurred: error: test failed! /builddir/build/BUILD/libreoffice-7.0.0.3/testtools/source/bridgetest/bridgetest.cxx:1176
> > error: error: test failed! /builddir/build/BUILD/libreoffice-7.0.0.3/testtools/source/bridgetest/bridgetest.cxx:1176
> > dying...make[1]: *** [/builddir/build/BUILD/libreoffice-7.0.0.3/testtools/CustomTarget_uno_test.mk:25: /builddir/build/BUILD/libreoffice-7.0.0.3/workdir/CustomTarget/testtools/uno_test.done] Error 1

(<https://koji.fedoraproject.org/koji/getfile?taskID=49136895&volume=DEFAULT
&name=build.log&offset=-4000>), so keep LTO disabled there until the issue is
addressed.

Note that for aarch64, armv7hl, and s390x %check is currently no-op, so it is
not obvious from just building the package whether or not they will have issues
with LTO at runtime.  But at least for ppc64le and x86_64 the (non--no-op)
%check has been seen to succeed with LTO enabled, including the
CppunitTest_sw_apitests for which LTO had originally been disabled for LO 6.4 in
5d644f1606 "%check fails with lto enabled" (see
<https://koji.fedoraproject.org/koji/taskinfo?taskID=49136767>).

libreoffice.spec

@@ -999,6 +999,12 @@ mv .git .git-rpm
 # path to external tarballs
 EXTSRCDIR=`dirname %{SOURCE0}`
 
+# On i686, CustomTarget_testtools/uno_test from the testsuite fails when LTO is
+# enabled:
+%ifarch i686
+%define _lto_cflags %{nil}
+%endif
+
 #use the RPM_OPT_FLAGS but remove the LibreOffice overridden ones
 for i in $RPM_OPT_FLAGS; do
         case "$i" in
@@ -1469,7 +1475,7 @@ done
 
 %check
 %ifnarch ppc64 s390x aarch64 armv7hl
-make
+make unitcheck slowcheck
 # we don't need this anymore
 rm -f %{buildroot}%{baseinstdir}/program/classes/smoketest.jar
 %endif