THRIFT-5109 Misc Cmake build improvements
Patch: Mario Emmenlauer

This closes #2017
This closes #2018
This closes #2019

- build/cmake/DefineInstallationPaths.cmake: fixed the library path
- build/cmake/ThriftMacros.cmake: do not enforce debug suffix 'd'
- lib/java/CMakeLists.txt: allow to override JAVA_INSTALL_DIR
diff --git a/build/cmake/DefinePlatformSpecifc.cmake b/build/cmake/DefinePlatformSpecifc.cmake
index c0bb529..f43f503 100644
--- a/build/cmake/DefinePlatformSpecifc.cmake
+++ b/build/cmake/DefinePlatformSpecifc.cmake
@@ -20,8 +20,8 @@
 # Uncomment this to show some basic cmake variables about platforms
 # include (NewPlatformDebug)
 
-# For Debug build types, append a "d" to the library names.
-set(CMAKE_DEBUG_POSTFIX "d" CACHE STRING "Set debug library postfix" FORCE)
+# For Debug build types, default to "d"-suffix in library names.
+set(CMAKE_DEBUG_POSTFIX "d" CACHE STRING "Set debug library postfix")
 
 # basic options
 foreach(lang IN ITEMS C CXX)