x86: enable PIE for dynamically linked executables

Compile all x86 programs on Android with -fPIE and -pie. This enables
PIE (Position Independent Executables), which helps protect Android
applications from exploitation due to memory management bugs.

Note 1: PIE *static* executables are not supported at this time and
require additional linker changes.

Note 2: This change compliments 026a85b129,
which was the exact same change, except for ARM.

Testing: Rebuilt the tree completely from scratch, and verified
that the system boots and basic functionality works in the emulator.

Change-Id: I990064c37da3d857e663b27f31fee05f689a2824

core/combo/TARGET_linux-x86.mk

@@ -73,7 +73,7 @@ TARGET_GLOBAL_CFLAGS += \
 			-Wa,--noexecstack \
 			-Werror=format-security \
 			-Wstrict-aliasing=2 \
-			-fPIC \
+			-fPIC -fPIE \
 			-ffunction-sections \
 			-finline-functions \
 			-finline-limit=300 \
@@ -158,6 +158,7 @@ $(hide) $(PRIVATE_CXX) \
 	-nostdlib -Bdynamic \
 	-Wl,-dynamic-linker,/system/bin/linker \
 	-Wl,-z,nocopyreloc \
+	-fPIE -pie \
 	-o $@ \
 	$(TARGET_GLOBAL_LD_DIRS) \
 	-Wl,-rpath-link=$(TARGET_OUT_INTERMEDIATE_LIBRARIES) \