ANDROID: kbuild: change LTO into a choice

This fixes allmodconfig and prepares for gcc's LTO support.

Bug: 67506682
Change-Id: Ied90f9f25293321287b25fd6f214f7f1913f44cb
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

arch/Kconfig

@@ -490,7 +490,7 @@ config LD_DEAD_CODE_DATA_ELIMINATION
 	  is used to distinguish them from label names / C identifiers.
 
 config LTO
-	bool
+	def_bool n
 
 config ARCH_SUPPORTS_LTO_CLANG
 	bool
@@ -500,6 +500,15 @@ config ARCH_SUPPORTS_LTO_CLANG
 	  - compiling inline assembly with clang's integrated assembler,
 	  - and linking with either lld or GNU gold w/ LLVMgold.
 
+choice
+	prompt "Link-Time Optimization (LTO) (EXPERIMENTAL)"
+	default LTO_NONE
+	help
+	  This option turns on Link-Time Optimization (LTO).
+
+config LTO_NONE
+	bool "None"
+
 config LTO_CLANG
 	bool "Use clang Link Time Optimization (LTO) (EXPERIMENTAL)"
 	depends on ARCH_SUPPORTS_LTO_CLANG
@@ -518,6 +527,8 @@ config LTO_CLANG
           5.0 (make CC=clang) and GNU gold from binutils >= 2.27, and have the
           LLVMgold plug-in in LD_LIBRARY_PATH.
 
+endchoice
+
 config CFI
 	bool