Fix echo blankline on windows

Makefile

@@ -75,7 +75,7 @@ help_usage:
 	@echo clean, clean_all:	Clean output from previous build for all available languages \(won\'t clean third party\).
 	@echo detect, detect_all:	Show variables used to build OR-Tools for all available languages.
 ifeq ($(SYSTEM),win)
-	@echo.
+	@echo off & echo(
 else
 	@echo
 endif

makefiles/Makefile.cpp.mk

@@ -4,7 +4,7 @@ help_cc:
 	@echo Use one of the following C++ targets:
 ifeq ($(SYSTEM),win)
 	@tools\grep.exe "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.cpp.mk | tools\sed.exe "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/"
-	@echo.
+	@echo off & echo(
 else
 	@grep "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.cpp.mk | sed "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/" | expand -t20
 	@echo
@@ -671,7 +671,7 @@ detect_cc:
 	@echo OR_TOOLS_LD_FLAGS = $(OR_TOOLS_LD_FLAGS)
 	@echo DEPENDENCIES_LNK = $(DEPENDENCIES_LNK)
 ifeq ($(SYSTEM),win)
-	@echo.
+	@echo off & echo(
 else
 	@echo
 endif

makefiles/Makefile.csharp.mk

@@ -4,7 +4,7 @@ help_csharp:
 	@echo Use one of the following C# targets:
 ifeq ($(SYSTEM),win)
 	@tools\grep.exe "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.csharp.mk | tools\sed.exe "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/"
-	@echo.
+	@echo off & echo(
 else
 	@grep "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.csharp.mk | sed "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/" | expand -t20
 	@echo
@@ -763,7 +763,7 @@ endif
 	@echo NUGET_COMPILER = $(NUGET_COMPILER)
 	@echo NUGET_EXECUTABLE = "$(NUGET_EXECUTABLE)"
 ifeq ($(SYSTEM),win)
-	@echo.
+	@echo off & echo(
 else
 	@echo
 endif

makefiles/Makefile.fsharp.mk

@@ -4,7 +4,7 @@ help_fsharp:
 	@echo Use one of the following F# targets:
 ifeq ($(SYSTEM),win)
 	@tools\grep.exe "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.fsharp.mk | tools\sed.exe "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/"
-	@echo.
+	@echo off & echo(
 else
 	@grep "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.fsharp.mk | sed "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/" | expand -t20
 	@echo
@@ -71,7 +71,7 @@ endif
 	@echo FSHARP_COMPILER = $(FSHARP_COMPILER)
 	@echo FSHARP_EXECUTABLE = "$(FSHARP_EXECUTABLE)"
 ifeq ($(SYSTEM),win)
-	@echo.
+	@echo off & echo(
 else
 	@echo
 endif

makefiles/Makefile.java.mk

@@ -4,7 +4,7 @@ help_java:
 	@echo Use one of the following Java targets:
 ifeq ($(SYSTEM),win)
 	@tools\grep.exe "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.java.mk | tools\sed.exe "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/"
-	@echo.
+	@echo off & echo(
 else
 	@grep "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.java.mk | sed "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/" | expand -t24
 	@echo
@@ -427,7 +427,7 @@ detect_java:
 	@echo JAR_BIN = $(JAR_BIN)
 	@echo JNIFLAGS = $(JNIFLAGS)
 ifeq ($(SYSTEM),win)
-	@echo.
+	@echo off & echo(
 else
 	@echo
 endif

makefiles/Makefile.port.mk

@@ -246,7 +246,7 @@ endif
 	@echo SWIG_BINARY = $(SWIG_BINARY)
 	@echo SWIG_INC = $(SWIG_INC)
 ifeq ($(SYSTEM),win)
-	@echo.
+	@echo off & echo(
 else
 	@echo
 endif

makefiles/Makefile.python.mk

@@ -4,7 +4,7 @@ help_python:
 	@echo Use one of the following Python targets:
 ifeq ($(SYSTEM),win)
 	@tools\grep.exe "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.python.mk | tools\sed.exe "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/"
-	@echo.
+	@echo off & echo(
 else
 	@grep "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.python.mk | sed "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/" | expand -t24
 	@echo
@@ -461,7 +461,7 @@ endif
 	@echo PYTHON_LNK = $(PYTHON_LNK)
 	@echo SWIG_PYTHON3_FLAG = $(SWIG_PYTHON3_FLAG)
 ifeq ($(SYSTEM),win)
-	@echo.
+	@echo off & echo(
 else
 	@echo
 endif

makefiles/Makefile.third_party.win.mk

@@ -2,7 +2,7 @@
 help_third_party:
 	@echo Use one of the following Prerequisite targets:
 	@tools\grep.exe "^.PHONY: .* #" $(CURDIR)/makefiles/Makefile.third_party.win.mk | tools\sed.exe "s/\.PHONY: \(.*\) # \(.*\)/\1\t\2/"
-	@echo.
+	@echo off & echo(
 
 # tags of dependencies to checkout.
 GFLAGS_TAG = 2.2.1