GH-33657: [C++] arrow-dataset.pc doesn't depend on parquet.pc without…

… ARROW_PARQUET=ON (#33665)

# Which issue does this PR close?

Closes #33657

# Rationale for this change

If `arrow-dataset.pc` has `parquet` in `Requires` without `ARROW_PARQUET=ON`, the `arrow-dataset.pc` is invalid.

# What changes are included in this PR?

This PR includes `ARROW_PARQUET=ON` check to determine suitable `Requires` value.

# Are these changes tested?

Yes.

# Are there any user-facing changes?

Yes. `arrow-dataset.pc` without `ARROW_PARQUET=ON` users can use `arrow-dataset.pc` with this.
* Closes: #33657

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

cpp/src/arrow/dataset/CMakeLists.txt

@@ -31,6 +31,12 @@ set(ARROW_DATASET_SRCS
     scanner.cc
     scan_node.cc)
 
+if(ARROW_PARQUET)
+  set(ARROW_DATASET_PKG_CONFIG_REQUIRES parquet)
+else()
+  set(ARROW_DATASET_PKG_CONFIG_REQUIRES arrow)
+endif()
+
 set(ARROW_DATASET_STATIC_LINK_LIBS)
 set(ARROW_DATASET_SHARED_LINK_LIBS)
 set(ARROW_DATASET_STATIC_INSTALL_INTERFACE_LIBS)

cpp/src/arrow/dataset/arrow-dataset.pc.in

@@ -22,6 +22,6 @@ libdir=@ARROW_PKG_CONFIG_LIBDIR@
 Name: Apache Arrow Dataset
 Description: Apache Arrow Dataset provides an API to read and write semantic datasets stored in different locations and formats.
 Version: @ARROW_VERSION@
-Requires: arrow parquet
+Requires: @ARROW_DATASET_PKG_CONFIG_REQUIRES@
 Libs: -L${libdir} -larrow_dataset
 Cflags.private: -DARROW_DS_STATIC