Revert "[cmake] Use `GNUInstallDirs` to support custom installation dirs."

https://lab.llvm.org/buildbot/#/builders/46/builds/21146 Still have
this odd error, not sure how to reproduce, so I will just try breaking
up my patch.

This reverts commit 4a678f8072004eff9214c1a4e1836a14abb69535.

3 files changed, 12 insertions, 16 deletions

diff --git a/polly/CMakeLists.txt b/polly/CMakeLists.txt
index d6bcc8f7f285..fb62dbd3a09b 100644
--- a/polly/CMakeLists.txt
+++ b/polly/CMakeLists.txt
@@ -1,5 +1,3 @@
-include(GNUInstallDirs)
-
 # Check if this is a in tree build.
 if (NOT DEFINED LLVM_MAIN_SRC_DIR)
   project(Polly)
@@ -126,13 +124,13 @@ include_directories(
 
 if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   install(DIRECTORY include/
-    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
+    DESTINATION include
     FILES_MATCHING
     PATTERN "*.h"
     )
 
   install(DIRECTORY ${POLLY_BINARY_DIR}/include/
-    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}"
+    DESTINATION include
     FILES_MATCHING
     PATTERN "*.h"
     PATTERN "CMakeFiles" EXCLUDE
diff --git a/polly/cmake/CMakeLists.txt b/polly/cmake/CMakeLists.txt
index 9b508941a139..524d6069c117 100644
--- a/polly/cmake/CMakeLists.txt
+++ b/polly/cmake/CMakeLists.txt
@@ -1,6 +1,5 @@
 # Keep this in sync with llvm/cmake/CMakeLists.txt!
 
-include(ExtendPath)
 include(FindPrefixFromConfig)
 
 set(LLVM_INSTALL_PACKAGE_DIR "lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
@@ -84,18 +83,17 @@ file(GENERATE
 # Generate PollyConfig.cmake for the install tree.
 unset(POLLY_EXPORTS)
 find_prefix_from_config(POLLY_CONFIG_CODE POLLY_INSTALL_PREFIX "${POLLY_INSTALL_PACKAGE_DIR}")
-extend_path(POLLY_CONFIG_LLVM_CMAKE_DIR "\${POLLY_INSTALL_PREFIX}" "${LLVM_INSTALL_PACKAGE_DIR}")
-extend_path(POLLY_CONFIG_CMAKE_DIR "\${POLLY_INSTALL_PREFIX}" "${POLLY_INSTALL_PACKAGE_DIR}")
-extend_path(POLLY_CONFIG_LIBRARY_DIRS "\${POLLY_INSTALL_PREFIX}" "lib${LLVM_LIBDIR_SUFFIX}")
-extend_path(base_includedir "\${POLLY_INSTALL_PREFIX}" "${CMAKE_INSTALL_INCLUDEDIR}")
+set(POLLY_CONFIG_LLVM_CMAKE_DIR "\${POLLY_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")
+set(POLLY_CONFIG_CMAKE_DIR "\${POLLY_INSTALL_PREFIX}/${POLLY_INSTALL_PACKAGE_DIR}")
+set(POLLY_CONFIG_LIBRARY_DIRS "\${POLLY_INSTALL_PREFIX}/lib${LLVM_LIBDIR_SUFFIX}")
 if (POLLY_BUNDLED_ISL)
   set(POLLY_CONFIG_INCLUDE_DIRS
-    "${base_includedir}"
-    "${base_includedir}/polly"
+    "\${POLLY_INSTALL_PREFIX}/include"
+    "\${POLLY_INSTALL_PREFIX}/include/polly"
     )
 else()
   set(POLLY_CONFIG_INCLUDE_DIRS
-    "${base_includedir}"
+    "\${POLLY_INSTALL_PREFIX}/include"
     ${ISL_INCLUDE_DIRS}
     )
 endif()
@@ -112,12 +110,12 @@ set(POLLY_EXPORTS
 foreach(tgt IN LISTS POLLY_CONFIG_EXPORTED_TARGETS)
   get_target_property(tgt_type ${tgt} TYPE)
   if (tgt_type STREQUAL "EXECUTABLE")
-    set(tgt_prefix "${CMAKE_INSTALL_BINDIR}/")
+    set(tgt_prefix "bin/")
   else()
-    set(tgt_prefix "${CMAKE_INSTALL_LIBDIR}/")
+    set(tgt_prefix "lib/")
   endif()
 
-  extend_path(tgt_path "\${POLLY_INSTALL_PREFIX}" "${tgt_prefix}$<TARGET_FILE_NAME:${tgt}>")
+  set(tgt_path "\${POLLY_INSTALL_PREFIX}/${tgt_prefix}$<TARGET_FILE_NAME:${tgt}>")
 
   if (NOT tgt_type STREQUAL "INTERFACE_LIBRARY")
     set(POLLY_EXPORTS
diff --git a/polly/lib/External/CMakeLists.txt b/polly/lib/External/CMakeLists.txt
index 2f912e7daeb2..e3a5683fccdc 100644
--- a/polly/lib/External/CMakeLists.txt
+++ b/polly/lib/External/CMakeLists.txt
@@ -290,7 +290,7 @@ if (POLLY_BUNDLED_ISL)
     install(DIRECTORY
       ${ISL_SOURCE_DIR}/include/
       ${ISL_BINARY_DIR}/include/
-      DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/polly"
+      DESTINATION include/polly
       FILES_MATCHING
       PATTERN "*.h"
       PATTERN "CMakeFiles" EXCLUDE