RFR: JDK-8179658 SetupProcessMarkdown creates long file names

[Magnus Ihse Bursie]

When building with a root directory with a very deep level, the fix in 
JDK-8179658 can cause the build to fail.

The temporary files created use the entire path, which was never 
intended. This patch fixes that.

Bug: https://bugs.openjdk.java.net/browse/JDK-8179658
Patch inline:
diff --git a/make/Javadoc.gmk b/make/Javadoc.gmk
--- a/make/Javadoc.gmk
+++ b/make/Javadoc.gmk
@@ -390,14 +390,14 @@
      $(eval SPECS_$m := $(call FindModuleSpecsDirs, $m)) \
      $(foreach d, $(SPECS_$m), \
        $(if $(filter %.md, $(call CacheFind, $d)), \
-        $(eval $(call SetupProcessMarkdown, CONVERT_MARKDOWN_$m_$d, \
+        $(eval $(call SetupProcessMarkdown, 
CONVERT_MARKDOWN_$m_$(patsubst $(TOPDIR)/%,%,$d), \
              SRC := $d, \
              FILES := $(filter %.md, $(call CacheFind, $d)), \
              DEST := $(JAVADOC_OUTPUTDIR)/specs/, \
              CSS := $(GLOBAL_SPECS_DEFAULT_CSS_FILE), \
          )) \
        ) \
-      $(eval JDK_SPECS_TARGETS += $(CONVERT_MARKDOWN_$m_$d)) \
+      $(eval JDK_SPECS_TARGETS += $(CONVERT_MARKDOWN_$m_$(patsubst 
$(TOPDIR)/%,%,$d))) \
      ) \
    )
  endif

/Magnus