libtracefs: support reproducible builds

[snip of Makefile]
 # bison will create both sqlhist.tab.c and sqlhist.tab.h
sqlhist.tab.h:
sqlhist.tab.c: sqlhist.y sqlhist.tab.h
    bison --debug -v --report-file=bison.report -d -o $@ $<
[snip]

sources of libtracefs is fetched by git, the mtime of sqlhist.y,
sqlhist.tab.c is random. so sometimes, sqlhist.tab.c is regenerated,
sometimes, sqlhist.tab.c in original sources in used. bison used to
gernerate sqlhist.tab.c by upstream libtracefs maybe has different
version with the build host one. This make the final libtracefs.so not
reproducible. This fix touch sqlhist.tab.c to make it has the newest
mtime, and sqlhist.tab.c is not regenerated during build.

Signed-off-by: Changqing Li <changqing.li@windriver.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-kernel/libtracefs/libtracefs_1.8.2.bb

@@ -16,6 +16,10 @@ SRC_URI = "git://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git;branch=${BP
 
 inherit pkgconfig bash-completion
 
+do_compile:prepend() {
+    touch ${S}/src/sqlhist.tab.c
+}
+
 do_install() {
     oe_runmake install DESTDIR=${D} pkgconfig_dir=${libdir}/pkgconfig
 }