RFR: JDK-8151300: Build shell trace functionality lost in JDK-8076060

[Erik Joelsson]

When running the build with LOG=trace, we (used to) have a neat feature 
that would print which prerequisites triggered each rule to run. This 
functionality was lost with JDK-8076060 where the SHELL variable setting 
this up was changed to be assigned using ':=' instead of ':'. I cannot 
see any reason this was done for this particular variable so assuming it 
was a mistake while changing other variables in the same file. Removing 
the ':' for SHELL fixes LOG=trace.


Bug: https://bugs.openjdk.java.net/browse/JDK-8151300
diff -r 83fe2455dcc1 make/common/MakeBase.gmk
--- a/make/common/MakeBase.gmk
+++ b/make/common/MakeBase.gmk
@@ -282,7 +282,7 @@
      # Default shell seems to always be /bin/sh. Must override with 
bash to get this to work on Solaris.
      # Only use time if it's GNU time which supports format and output 
file.
      WRAPPER_SHELL := $$(BASH) $$(SRC_ROOT)/common/bin/shell-tracer.sh 
$$(if $$(findstring yes,$$(IS_GNU_TIME)),$$(TIME),-) 
$$(OUTPUT_ROOT)/build-trace-time.log $$(SHELL)
-    SHELL := $$(warning $$(if $$@,Building $$@,Running shell command) 
$$(if $$<, (from $$<))$$(if $$?, ($$(wordlist 1, 20, $$?) $$(if 
$$(wordlist 21, 22, $$?), ... [in total $$(words $$?) files]) 
newer)))$$(WRAPPER_SHELL)
+    SHELL = $$(warning $$(if $$@,Building $$@,Running shell command) 
$$(if $$<, (from $$<))$$(if $$?, ($$(wordlist 1, 20, $$?) $$(if 
$$(wordlist 21, 22, $$?), ... [in total $$(words $$?) files]) 
newer)))$$(WRAPPER_SHELL)
    endif
    # The warn level can never be turned off
    LogWarn = $$(info $$(strip $$1))


/Erik