[PATCH LIVEPATCH-BUILD-TOOLS 2/2] Prevent spurious rebuilding

[Ross Lagerwall <ross.lagerwall@citrix.com>]

Don't change the timestamp of arch/x86/Makefile when editing it since it
forces much of the Xen tree to be rebuilt and then requires many
invocations of create-diff-tool.

This is safe since the Makefile change only changes the final link rule,
and xen will be relinked anyway.
---
 livepatch-build | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/livepatch-build b/livepatch-build
index d9d9da3..c057fa1 100755
--- a/livepatch-build
+++ b/livepatch-build
@@ -98,10 +98,13 @@ function build_special()
     # Build with special GCC flags
     cd "${SRCDIR}/xen" || die
     sed -i 's/CFLAGS += -nostdinc/CFLAGS += -nostdinc -ffunction-sections -fdata-sections/' Rules.mk
+    cp -p arch/x86/Makefile arch/x86/Makefile.bak
     sed -i 's/--section-alignment=0x200000/--section-alignment=0x1000/' arch/x86/Makefile
+    # Restore timestamps to prevent spurious rebuilding
+    touch --reference=arch/x86/Makefile.bak arch/x86/Makefile
     make "-j$CPUS" $XEN_DEBUG &> "${OUTPUT}/build_${name}_compile.log" || die
     sed -i 's/CFLAGS += -nostdinc -ffunction-sections -fdata-sections/CFLAGS += -nostdinc/' Rules.mk
-    sed -i 's/--section-alignment=0x1000/--section-alignment=0x200000/' arch/x86/Makefile
+    mv -f arch/x86/Makefile.bak arch/x86/Makefile
 
     unset LIVEPATCH_BUILD_DIR
     unset LIVEPATCH_CAPTURE_DIR
-- 
2.7.4


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