use gcc 4.8.5 for c6x, enable static libgcc for DSBT binary format

target/config/Config.in.gcc

@@ -6,7 +6,7 @@ prompt "GCC version"
 default ADK_TOOLCHAIN_GCC_4_2_4 if ADK_TARGET_ARCH_METAG
 default ADK_TOOLCHAIN_GCC_4_4_7 if ADK_TARGET_ARCH_AVR32
 default ADK_TOOLCHAIN_GCC_4_5_4 if ADK_TARGET_ARCH_BFIN
-default ADK_TOOLCHAIN_GCC_4_7_4 if ADK_TARGET_ARCH_C6X
+default ADK_TOOLCHAIN_GCC_4_8_5 if ADK_TARGET_ARCH_C6X
 default ADK_TOOLCHAIN_GCC_4_8_ARC if ADK_TARGET_ARCH_ARC
 default ADK_TOOLCHAIN_GCC_4_9_OR1K_UCLIBC_NG if ADK_TARGET_ARCH_OR1K && ADK_TARGET_LIB_UCLIBC_NG
 default ADK_TOOLCHAIN_GCC_5_2_OR1K_MUSL if ADK_TARGET_ARCH_OR1K && ADK_TARGET_LIB_MUSL
@@ -48,7 +48,6 @@ config ADK_TOOLCHAIN_GCC_4_8_5
 	depends on !ADK_TARGET_ARCH_AVR32
 	depends on !ADK_TARGET_ARCH_CRIS
 	depends on !ADK_TARGET_ARCH_TILE
-	depends on !ADK_TARGET_ARCH_C6X
 	depends on !ADK_TARGET_ARCH_H8300
 	depends on !ADK_TARGET_ARCH_METAG
 	depends on !ADK_TARGET_ARCH_OR1K
@@ -76,7 +75,6 @@ config ADK_TOOLCHAIN_GCC_4_7_4
 	depends on !ADK_TARGET_ARCH_AVR32
 	depends on !ADK_TARGET_ARCH_CRIS
 	depends on !ADK_TARGET_ARCH_TILE
-	depends on !ADK_TARGET_ARCH_C6X
 	depends on !ADK_TARGET_ARCH_H8300
 	depends on !ADK_TARGET_ARCH_METAG
 	depends on !ADK_TARGET_ARCH_OR1K

toolchain/gcc/Makefile

@@ -67,7 +67,7 @@ ifeq ($(ADK_TARGET_LIB_WITHOUT_THREADS)$(ADK_TARGET_WITHOUT_THREADS),y)
 GCC_FINAL_CONFOPTS:=	--disable-tls --disable-threads --disable-libatomic
 endif
 
-ifeq ($(ADK_TARGET_BINFMT_FLAT)$(ADK_TARGET_USE_STATIC_LIBS),y)
+ifeq ($(ADK_TARGET_BINFMT_FLAT)$(ADK_TARGET_USE_STATIC_LIBS)$(ADK_TARGET_BINFMT_DSBT),y)
 GCC_FINAL_CONFOPTS+=	--disable-shared
 else
 # uClibc/glibc uses libgcc_s.so.1 for pthread_cancel with dlopen