[PkgConfig] add tests to ensure that it handles correctly circular deps

Author: Adam-le-dev

Tests/TSCUtilityTests/PkgConfigParserTests.swift

@@ -15,6 +15,11 @@ import TSCTestSupport
 @testable import TSCUtility
 
 final class PkgConfigParserTests: XCTestCase {
+    func testCircularPCFile() throws {
+        XCTAssertTrue(try PkgConfig(name: "harfbuzz", additionalSearchPaths: [pcFilePath("harfbuzz.pc")], diagnostics: DiagnosticsEngine(), brewPrefix: nil).diagnostics.diagnostics.contains { diagnostic in
+            diagnostic.message.text == "circular dependency detected while parsing harfbuzz: harfbuzz -> freetype2 -> harfbuzz"
+        })
+    }
 
     func testGTK3PCFile() {
         try! loadPCFile("gtk+-3.0.pc") { parser in

Tests/TSCUtilityTests/pkgconfigInputs/freetype2.pc

@@ -0,0 +1,14 @@
+prefix=/usr
+exec_prefix=/usr
+libdir=/usr/lib
+includedir=/usr/include
+
+Name: FreeType 2
+URL: https://freetype.org
+Description: A free, high-quality, and portable font engine.
+Version: 23.4.17
+Requires:
+Requires.private: zlib, libpng, harfbuzz >= 1.8.0
+Libs: -L${libdir} -lfreetype
+Libs.private: -lbz2
+Cflags: -I${includedir}/freetype2

Tests/TSCUtilityTests/pkgconfigInputs/harfbuzz.pc

@@ -0,0 +1,11 @@
+prefix=/usr
+libdir=${prefix}/lib
+includedir=${prefix}/include
+
+Name: harfbuzz
+Description: HarfBuzz text shaping library
+Version: 2.7.4
+Requires.private: freetype2, graphite2, glib-2.0
+Libs: -L${libdir} -lharfbuzz
+Libs.private: -pthread -lm
+Cflags: -I${includedir}/harfbuzz