Fix boost build

Normal libreoffice way to add a file is to put that in makefile.mk into ADDITIONAL_FILES list
which creates a file with "dummy" as content and then to patch that file with the real content.
This prevents a patching hell if timestamps change and boost is unpacked again

boost/boost_1_39_0.patch

@@ -285,9 +285,10 @@ index 5d75be2..730cf0c 100644
                  ).second;
              }
  
---- /dev/null
+--- misc/build/boost_1_39_0/libs/thread/src/win32/makefile.mk
 +++ misc/build/boost_1_39_0/libs/thread/src/win32/makefile.mk
-@@ -0,0 +1,21 @@
+@@ -1,1 +1,21 @@
+-dummy
 +PRJ=..$/..$/..$/..$/..$/..$/..$/..
 +
 +PRJNAME=boostthread

boost/makefile.mk

@@ -52,6 +52,9 @@ TARFILE_NAME=boost_1_39_0
 TARFILE_MD5=fcc6df1160753d0b8c835d17fdeeb0a7
 PATCH_FILES=$(TARFILE_NAME).patch
 
+ADDITIONAL_FILES= \
+    libs/thread/src/win32/makefile.mk
+
 CONFIGURE_DIR=
 CONFIGURE_ACTION=