src: Fix to build libibus-1.0.la twice

The purpose of autotools is to automatically handle dependencies. By
calling $(MAKE) manually and without specifying any dependencies below,
we are going out of our way to prevent automake from doing its job.

    ibusunicodegen.h:
           $(MAKE) $(AM_MAKEFLAGS) dicts/unicode-blocks.dict

This avoids a build error whereby libibus-1.0.la is built twice
simultaneously, races with itself, and breaks the build.

    dicts/unicode-blocks.dict ibusunicodegen.h: unicode-parser

The two build targets let `make ibusunicodegen.h` try to make
`dicts/unicode-blocks.dict` and `ibusunicodegen.h` with unicode-parser.

Unlike `ibusunicodegen.h`, we cannot add `ibusemojigen.h` to the rule
that produces it (as a side-effect) because the rule is specified with
GNU Make syntax:

    dicts/emoji-%.dict: emoji-parser

and doing so yields an error:

    config.status: error: Something went wrong bootstrapping makefile
        fragments for automatic dependency tracking.  If GNU make was
        not used, consider re-running the configure script with
        MAKE="gmake" (or whatever is necessary).  You can also try
        re-running configure with the '--disable-dependency-tracking'
        option to at least be able to build the package (albeit without
        support for automatic dependency tracking).

So instead, add a prerequisite to the rule.

Both emoji-parser and unicode-parser has $(libibus) in LDADD
and $(libibus) is built before emoji-parser and unicode-parser are
built.

BUG=#2523

src/Makefile.am

@@ -372,8 +372,9 @@ dicts/emoji-%.dict: emoji-parser
 	    echo "Skip $$plus_comment $@"; \
 	fi;
 
-ibusemojigen.h:
-	$(MAKE) $(AM_MAKEFLAGS) dicts/emoji-en.dict
+# #2523 Should use autotool dependency
+ibusemojigen.h: dicts/emoji-en.dict
+	$(MAKE) $(AM_MAKEFLAGS) $^
 
 # We put dicts/emoji-%.dict as the make target for the parallel build
 # and the make target has to be genarated even if the file size is zero.
@@ -424,7 +425,8 @@ dicts/unicode-names.dict: unicode-parser
 	    echo "Generated $@"; \
 	fi;
 
-dicts/unicode-blocks.dict: unicode-parser
+# #2523 Should use autotool dependency
+dicts/unicode-blocks.dict ibusunicodegen.h: unicode-parser
 	$(AM_V_at)input_file="$(UCD_DIR)/Blocks.txt"; \
 	if test ! -f "$$input_file" ; then \
 	    echo "WARNING: Not found $$input_file" 1>&2; \
@@ -436,9 +438,6 @@ dicts/unicode-blocks.dict: unicode-parser
 	    echo "Generated $@"; \
 	fi;
 
-ibusunicodegen.h:
-	$(MAKE) $(AM_MAKEFLAGS) dicts/unicode-blocks.dict
-
 unicode_parser_SOURCES =        \
     unicode-parser.c            \
     $(parser_extra_sources)     \