tesseract-lang.inc: set ${S} to fix the QA warning

The ${S} is not set in the recipe cause the QA warning:
WARNING: tesseract-lang-eng: the directory ${WORKDIR}/${BP}
(/buildarea2/build/tmp/work/all-poky-linux/tesseract-lang-eng/3.02-r0/tesseract-lang-eng-3.02)
pointed to by the S variable doesn't exist - please set S within the recipe to point to where the source has been unpacked to

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>

meta-oe/recipes-graphics/tesseract/tesseract-lang.inc

@@ -3,11 +3,13 @@ LIC_FILES_CHKSUM = "file://${COREBASE}/meta/files/common-licenses/Apache-2.0;md5
 
 SRC_URI = "https://tesseract-ocr.googlecode.com/files/tesseract-ocr-${PV}.${TESSERACT_LANG}.tar.gz"
 
+S = "${WORKDIR}/tesseract-ocr"
+
 inherit allarch
 
 do_install() {
     install -d ${D}${datadir}/tessdata
-    cp ${WORKDIR}/tesseract-ocr/tessdata/${TESSERACT_LANG}.traineddata ${D}${datadir}/tessdata
+    cp ${S}/tessdata/${TESSERACT_LANG}.traineddata ${D}${datadir}/tessdata
 }
 
 FILES_${PN} += "${datadir}/tessdata"