[CMake] Remove {LIBCXX,LIBCXXABI,LIBUNWIND}_INSTALL_PREFIX

These variables were introduced during early work on the runtimes build
but were obsoleted by {LIBCXX,LIBCXXABI,LIBUNWIND}_INSTALL_LIBRARY_DIR.

Differential Revision: https://reviews.llvm.org/D99697

GitOrigin-RevId: 96d8c6b571e696f520a054820d13872cdc17c793
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 036f39b..1621d37 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -425,9 +425,6 @@
 
 file(MAKE_DIRECTORY "${LIBCXX_BINARY_INCLUDE_DIR}")
 
-set(LIBCXX_INSTALL_PREFIX "" CACHE STRING "Define libc++ destination prefix.")
-set(LIBCXX_INSTALL_HEADER_PREFIX "" CACHE STRING "Define libc++ header destination prefix.")
-
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${LIBCXX_LIBRARY_DIR})
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${LIBCXX_LIBRARY_DIR})
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${LIBCXX_LIBRARY_DIR})
diff --git a/cmake/Modules/HandleLibCXXABI.cmake b/cmake/Modules/HandleLibCXXABI.cmake
index fdd5c7f..987bb40 100644
--- a/cmake/Modules/HandleLibCXXABI.cmake
+++ b/cmake/Modules/HandleLibCXXABI.cmake
@@ -63,7 +63,7 @@
 
         if (LIBCXX_INSTALL_HEADERS)
           install(FILES "${LIBCXX_BINARY_INCLUDE_DIR}/${fpath}"
-            DESTINATION ${LIBCXX_INSTALL_HEADER_PREFIX}include/c++/v1/${dstdir}
+            DESTINATION include/c++/v1/${dstdir}
             COMPONENT cxx-headers
             PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
             )
diff --git a/docs/BuildingLibcxx.rst b/docs/BuildingLibcxx.rst
index bf80c6d..24e0a4c 100644
--- a/docs/BuildingLibcxx.rst
+++ b/docs/BuildingLibcxx.rst
@@ -235,12 +235,6 @@
   Extra suffix to append to the directory where libraries are to be installed.
   This option overrides `LLVM_LIBDIR_SUFFIX`.
 
-.. option:: LIBCXX_INSTALL_PREFIX:STRING
-
-  **Default**: ``""``
-
-  Define libc++ destination prefix.
-
 .. option:: LIBCXX_HERMETIC_STATIC_LIBRARY:BOOL
 
   **Default**: ``OFF``
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index daf504e..4c7fd86 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -219,7 +219,7 @@
   foreach(file ${files})
     get_filename_component(dir ${file} DIRECTORY)
     install(FILES ${file}
-      DESTINATION ${LIBCXX_INSTALL_HEADER_PREFIX}include/c++/v1/${dir}
+      DESTINATION include/c++/v1/${dir}
       COMPONENT cxx-headers
       PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
     )
@@ -227,7 +227,7 @@
 
   # Install the generated __config_site.
   install(FILES ${LIBCXX_GENERATED_INCLUDE_DIR}/__config_site
-    DESTINATION ${LIBCXX_INSTALL_HEADER_PREFIX}include/c++/v1
+    DESTINATION include/c++/v1
     PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
     COMPONENT cxx-headers)
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 015f2a9..7568b39 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -366,30 +366,30 @@
 
 if (LIBCXX_INSTALL_SHARED_LIBRARY)
   install(TARGETS cxx_shared
-    ARCHIVE DESTINATION ${LIBCXX_INSTALL_PREFIX}${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
-    LIBRARY DESTINATION ${LIBCXX_INSTALL_PREFIX}${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
-    RUNTIME DESTINATION ${LIBCXX_INSTALL_PREFIX}bin COMPONENT cxx)
+    ARCHIVE DESTINATION ${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
+    LIBRARY DESTINATION ${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
+    RUNTIME DESTINATION bin COMPONENT cxx)
 endif()
 
 if (LIBCXX_INSTALL_STATIC_LIBRARY)
   install(TARGETS cxx_static
-    ARCHIVE DESTINATION ${LIBCXX_INSTALL_PREFIX}${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
-    LIBRARY DESTINATION ${LIBCXX_INSTALL_PREFIX}${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
-    RUNTIME DESTINATION ${LIBCXX_INSTALL_PREFIX}bin COMPONENT cxx)
+    ARCHIVE DESTINATION ${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
+    LIBRARY DESTINATION ${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
+    RUNTIME DESTINATION bin COMPONENT cxx)
 endif()
 
 if(LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY)
   install(TARGETS cxx_experimental
-    LIBRARY DESTINATION ${LIBCXX_INSTALL_PREFIX}${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
-    ARCHIVE DESTINATION ${LIBCXX_INSTALL_PREFIX}${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
-    RUNTIME DESTINATION ${LIBCXX_INSTALL_PREFIX}bin COMPONENT cxx)
+    LIBRARY DESTINATION ${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
+    ARCHIVE DESTINATION ${LIBCXX_INSTALL_LIBRARY_DIR} COMPONENT cxx
+    RUNTIME DESTINATION bin COMPONENT cxx)
 endif()
 
 # NOTE: This install command must go after the cxx install command otherwise
 # it will not be executed after the library symlinks are installed.
 if (LIBCXX_ENABLE_SHARED AND LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
   install(FILES "$<TARGET_LINKER_FILE:cxx_shared>"
-    DESTINATION ${LIBCXX_INSTALL_PREFIX}${LIBCXX_INSTALL_LIBRARY_DIR}
+    DESTINATION ${LIBCXX_INSTALL_LIBRARY_DIR}
     COMPONENT libcxx)
 endif()