build: add additional search paths for Foundation artifacts

This allows us to homogenise the foundation build artifacts with
swift-tools-support-core, swift-driver, swift-package-manager,
swift-numerics, swift-argument-parser.

Author: compnerd

utils/build-script-impl

@@ -1934,13 +1934,15 @@ for host in "${ALL_HOSTS[@]}"; do
                     DOTEST_EXTRA="${DOTEST_EXTRA} -L${FOUNDATION_BUILD_DIR}/Sources/Foundation"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -L${FOUNDATION_BUILD_DIR}/Sources/FoundationNetworking"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -L${FOUNDATION_BUILD_DIR}/Sources/FoundationXML"
+                    DOTEST_EXTRA="${DOTEST_EXTRA} -L${FOUNDATION_BUILD_DIR}/lib"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -Xlinker -rpath -Xlinker ${LIBDISPATCH_BUILD_DIR}"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -Xlinker -rpath -Xlinker ${LIBDISPATCH_BUILD_DIR}/src"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -Xlinker -rpath -Xlinker ${FOUNDATION_BUILD_DIR}"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -Xlinker -rpath -Xlinker ${FOUNDATION_BUILD_DIR}/Foundation"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -Xlinker -rpath -Xlinker ${FOUNDATION_BUILD_DIR}/Sources/Foundation"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -Xlinker -rpath -Xlinker ${FOUNDATION_BUILD_DIR}/Sources/FoundationNetworking"
                     DOTEST_EXTRA="${DOTEST_EXTRA} -Xlinker -rpath -Xlinker ${FOUNDATION_BUILD_DIR}/Sources/FoundationXML"
+                    DOTEST_EXTRA="${DOTEST_EXTRA} -Xlinker -rpath -Xlinker ${FOUNDATION_BUILD_DIR}/lib"
                 fi
 
                 # Watchpoint testing is currently disabled: see rdar://38566150.