autotools: fix --with-ca-embed build rule

Add missing rule dependency on the user-specified CA bundle. This fixes
including it when using the curl distro tarball, and other cases.

Also:
- fix the internal name of the CA bundle to avoid nested quotes.
  It broke broke the rule dependency for the make tool.
- exclude the generated (empty) `tool_ca_embed.c` file from the distro
  tarball.
  Patch-by: Daniel Stenberg

Follow-up to 8a3740bc8e #14059
Reported-by: rampageX on github
Fixes #14879
Closes #14882

acinclude.m4

@@ -1360,7 +1360,7 @@ AS_HELP_STRING([--without-ca-embed], [Don't embed a default CA bundle]),
 
   CURL_CA_EMBED=''
   if test "x$want_ca_embed" != "xno" -a "x$want_ca_embed" != "xunset" -a -f "$want_ca_embed"; then
-    CURL_CA_EMBED='"'$want_ca_embed'"'
+    CURL_CA_EMBED="$want_ca_embed"
     AC_SUBST(CURL_CA_EMBED)
     AC_MSG_RESULT([$want_ca_embed])
   else

src/Makefile.am

@@ -140,7 +140,7 @@ CLEANFILES += $(CA_EMBED_CSOURCE)
 if CURL_CA_EMBED_SET
 AM_CPPFLAGS += -DCURL_CA_EMBED
 MK_FILE_EMBED = $(top_srcdir)/src/mk-file-embed.pl
-$(CA_EMBED_CSOURCE): $(MK_FILE_EMBED)
+$(CA_EMBED_CSOURCE): $(MK_FILE_EMBED) $(CURL_CA_EMBED)
 	$(PERL) $(MK_FILE_EMBED) --var curl_ca_embed < $(CURL_CA_EMBED) > $(CA_EMBED_CSOURCE)
 else
 $(CA_EMBED_CSOURCE):
@@ -174,3 +174,6 @@ if HAVE_WINDRES
 .rc.o:
 	$(RC) -I$(top_srcdir)/include -DCURL_EMBED_MANIFEST $(RCFLAGS) -i $< -o $@
 endif
+
+dist-hook:
+	rm -f $(distdir)/$(CA_EMBED_CSOURCE)