Update build.sh

修复一处图片路径错误

Author: rzhb

ebook/build.sh

@@ -51,6 +51,6 @@ mkdir -p $TMP/images
 cp -r $WORKDIR/images/* $TMP/images/
 ls [0-9]*.html | xargs $SED -i "s/png?raw=true/png/g"
 
-pandoc --reference-links -S --toc -f html -t epub --epub-metadata=metadata.txt --epub-cover-image="$WORKDIR/../images/cover.png" -o "$WORKDIR/../build-web-application-with-golang.epub" `ls [0-9]*.html | sort`
+pandoc --reference-links -S --toc -f html -t epub --epub-metadata=metadata.txt --epub-cover-image="$WORKDIR/images/cover.png" -o "$WORKDIR/../build-web-application-with-golang.epub" `ls [0-9]*.html | sort`
 
 echo "$MSG_SUCCESSFULLY_GENERATED"