add test for deduplication bug

tests/functional/cases/report/report_duplicates.fts

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+
+# RUN: bash %s %T/report_duplicates
+# RUN: cd %T/report_duplicates; %{analyze-build} --output . --keep-empty --cdb input.json | ./check_exists.sh
+
+set -o errexit
+set -o nounset
+set -o xtrace
+
+# the test creates a subdirectory inside output dir.
+#
+# ${root_dir}
+# ├── input.json
+# ├── check_exists.sh
+# ├── check_not_exists.sh
+# └── src
+#    └── broken.c
+
+root_dir=$1
+mkdir -p "${root_dir}/src"
+
+cp "${test_input_dir}/div_zero.c" "${root_dir}/src/broken.c"
+
+cat > "${root_dir}/input.json" << EOF
+[
+    {
+        "directory": "${root_dir}",
+        "file": "${root_dir}/src/broken.c",
+        "command": "cc -c -o src/broken.o src/broken.c"
+    },
+    {
+        "directory": "${root_dir}",
+        "file": "${root_dir}/src/broken.c",
+        "command": "cc -c -o src/broken.o -Dthose=these src/broken.c"
+    }
+]
+EOF
+
+check_one="${root_dir}/check_exists.sh"
+cat > "${check_one}" << EOF
+#!/usr/bin/env bash
+
+set -o errexit
+set -o nounset
+set -o xtrace
+
+out_dir=\$(sed -n 's/\(.*\) Report directory created: \(.*\)/\2/p')
+if [ ! -d "\$out_dir" ]
+then
+    echo "output directory should exists"
+    false
+else
+    count=\$(grep broken "\$out_dir/index.html" | wc -l)
+    if [ \$((\$count)) -ne 1 ]
+    then
+        echo "\$out_dir does not contains 1 report entry";
+        false
+    fi
+fi
+EOF
+chmod +x "${check_one}"