Prefer CMake's built-in -fPIC and -fpie support

CMake has a built-in property, `POSITION_INDEPENDENT_CODE`, that determines
if code will be built with `-fPIC`. This property is `True` by default for
`SHARED` and `MODULE` library targets and `False` otherwise. Previously,
we were always passing the `-fPIC` flag manually. With this change, we set
the appropriate CMake variable that will enable the property for all
compile jobs.

Furthermore, with CMake policy CMP0083 set to "new" (which happens by
default when the `cmake_minimum_required` version is >=3.14), CMake has
built-in support for passing the `-fpie` flag when building executables. It
uses the same property, `POSITION_INDEPENDENT_CODE`, so setting this
property (and enabling it with the CMake `CheckPIESupported` module) allows
us to use CMake's built-in support for these flags.

Signed-off-by: Chris Burel <burelc@amazon.com>

cmake/Platform/Common/Clang/Configurations_clang.cmake

@@ -20,8 +20,6 @@ ly_append_configurations_options(
         -Wall
         -Werror
 
-        -fpie                   # Position-Independent Executables
-
         ###################
         # Disabled warnings (please do not disable any others without first consulting sig-build)
         ###################

cmake/Platform/Common/Configurations_common.cmake

@@ -62,3 +62,8 @@ if(CMAKE_GENERATOR MATCHES "Ninja")
         ly_set(CMAKE_JOB_POOL_LINK link_job_pool)
     endif()
 endif()
+
+set(CMAKE_POSITION_INDEPENDENT_CODE True)
+
+include(CheckPIESupported)
+check_pie_supported()

cmake/Platform/Linux/Configurations_linux.cmake

@@ -16,7 +16,6 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
             __linux__
             LINUX64
         COMPILATION
-            -fPIC
             -msse4.1
         LINK_NON_STATIC
             -Wl,-undefined,error
@@ -47,7 +46,6 @@ elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
             __linux__
             LINUX64
         COMPILATION
-            -fPIC
             -msse4.1
         LINK_NON_STATIC
             ${LY_GCC_GCOV_LFLAGS}