[MinGW] Restore the original Scintilla makefile

For the sake of maintenance of Scintilla (future update), we try to not modify Scintilla project, or at least minimize its modification.
Hence the compiling boost part is shifted to Notepad++ project.

Fix #11014, close #11485

PowerEditor/gcc/makefile

@@ -116,7 +116,6 @@ LEXILLA_TARGET_PATH := ../../PowerEditor/gcc/$(LEXILLA_TARGET)
 LEXILLA_BUILD_DIRECTORY := $(BUILD_DIRECTORY)/_lexilla.build
 LEXILLA_BUILD_PATH := ../../PowerEditor/gcc/$(LEXILLA_BUILD_DIRECTORY)
 
-
 LD_PATH += $(BUILD_DIRECTORY)
 
 # detect a build outside of PowerEditor/gcc and update dependent variables
@@ -226,7 +225,7 @@ $(LEXILLA_TARGET): .force
 endif
 
 $(SCINTILLA_TARGET): | $(BUILD_DIRECTORY) $(SCINTILLA_BUILD_DIRECTORY)
-	$(AT)$(MAKE) $(SUBMAKEFLAGS) -C $(SCINTILLA_DIRECTORY)/win32 DIR_O=$(SCINTILLA_BUILD_PATH) LIBSCI=$(SCINTILLA_TARGET_PATH) $(SCINTILLA_TARGET_PATH)
+	$(AT)$(MAKE) $(SUBMAKEFLAGS) -C $(SCINTILLA_DIRECTORY)/win32 -f makefile -f ../../boostregex/nppSpecifics_mingw.mak DIR_O=$(SCINTILLA_BUILD_PATH) LIBSCI=$(SCINTILLA_TARGET_PATH) $(SCINTILLA_TARGET_PATH)
 
 $(LEXILLA_TARGET): | $(BUILD_DIRECTORY) $(LEXILLA_BUILD_DIRECTORY)
 	$(AT)$(MAKE) $(SUBMAKEFLAGS) -C $(LEXILLA_DIRECTORY)/src DIR_O=$(LEXILLA_BUILD_PATH) LIBLEXILLA=$(LEXILLA_TARGET_PATH) $(LEXILLA_TARGET_PATH)

boostregex/nppSpecifics_mingw.mak

@@ -1,25 +1,26 @@
-# This makefile should be included in the main scintilla.mak file,
-# just after where LOBJS is defined (around line
-#
-# The following line should be added around line 211 of scintilla.mak
-# !INCLUDE nppSpecifics.mak
+# This makefile should be listed after main Scintilla makefile
+# by using the -f option for both makefiles
 
 # Set your boost path (the root of where you've unpacked your boost zip).
 # Boost is available from www.boost.org
 
 
-SRC_OBJS+=\
-	$(DIR_O)/BoostRegexSearch.o \
-	$(DIR_O)/UTF8DocumentIterator.o
+DIR_BOOST = ../../boostregex
+
+vpath %.h $(DIR_BOOST)
+vpath %.cxx $(DIR_BOOST)
 
-INCLUDES+= -I../../boostregex
+INCLUDES += -I $(DIR_BOOST)
+CXXFLAGS += -DSCI_OWNREGEX
 
-CXXFLAGS+= -DSCI_OWNREGEX
+BOOST_OBJS = \
+	$(DIR_O)/BoostRegExSearch.o \
+	$(DIR_O)/UTF8DocumentIterator.o
 
+$(BOOST_OBJS): $(DIR_O)/%.o: %.cxx
+	$(CXX) $(CXX_ALL_FLAGS) $(CXXFLAGS) -MMD -c $< -o $@
 
-$(DIR_O)/UTF8DocumentIterator.o:: ../../boostregex/UTF8DocumentIterator.cxx
-	$(CXX) $(CXX_ALL_FLAGS) $(CXXFLAGS) -D_SILENCE_ALL_CXX17_DEPRECATION_WARNINGS -c $< -o $@
+$(LIBSCI): $(BOOST_OBJS)
 
-$(DIR_O)/BoostRegexSearch.o:: ../../boostregex/BoostRegexSearch.cxx ../src/CharClassify.h ../src/RESearch.h
-	$(CXX) $(CXX_ALL_FLAGS) $(CXXFLAGS) -D_SILENCE_ALL_CXX17_DEPRECATION_WARNINGS -c $< -o $@
+-include $(BOOST_OBJS:.o=.d)
 

scintilla/win32/makefile

@@ -113,9 +113,6 @@ SRC_OBJS = \
 	$(DIR_O)/ViewStyle.o \
 	$(DIR_O)/XPM.o
 
-# To have PCRE boost regex with header only is integrated and not just the one from std
-include ../../boostregex/nppSpecifics_mingw.mak
-
 COMPONENT_OBJS = \
 	$(SRC_OBJS) \
 	$(DIR_O)/HanjaDic.o \