refactor(generate_json): use multiline strings in `generate_json.sh`

Using multiline strings (delimited by `EOF` on each side) means the
contents of the json file can be inserted verbatim into
`generate_json.sh`, rather than inserting escape codes (`\t` and `\n`)
manually.

Signed-off-by: Karl Meakin <karl.meakin@arm.com>
Change-Id: I85b8287712ea4cb99e70c58482df0d886b780dde
diff --git a/Makefile b/Makefile
index 0a1ae9e..97afc34 100644
--- a/Makefile
+++ b/Makefile
@@ -234,7 +234,7 @@
 # the options defined in the Makefile
 COMMON_CFLAGS 		+=	${CFLAGS} ${INCLUDES}
 
-COMMON_LDFLAGS		+=	--fatal-warnings -O1 --gc-sections --build-id=none
+COMMON_LDFLAGS		+=	${LDFLAGS} --fatal-warnings -O1 --gc-sections --build-id=none
 
 CC			:=	${CROSS_COMPILE}gcc
 CPP			:=	${CROSS_COMPILE}cpp