Fix gawk regexp escape sequence warning

Fix issue #1206: Replace [^\#] with [^\043] in AWK regex patterns.

The original [^\#] caused a gawk warning:
  'regexp escape sequence `#' is not a known regexp operator'

The initial fix of changing to [^#] broke the build because Make
interprets # as a comment character, truncating the command.

This fix uses the octal escape sequence \043 (ASCII code for #)
which:
1. Is properly escaped for Make (not interpreted as comment)
2. Is a valid AWK/regex escape sequence (no warning)
3. Works with both gawk and mawk

Changes:
- src/Makefile.shlib: 5 occurrences updated
- src/backend/Makefile: 2 occurrences updated

Author: zhan7236

src/Makefile.shlib

@@ -130,7 +130,7 @@ ifeq ($(PORTNAME), darwin)
     DLSUFFIX		= .so
     LINK.shared		= $(COMPILER) -bundle -multiply_defined suppress
   endif
-  BUILD.exports		= $(AWK) '/^[^\#]/ {printf "_%s\n",$$1}' $< >$@
+  BUILD.exports		= $(AWK) '/^[^\043]/ {printf "_%s\n",$$1}' $< >$@
   exports_file		= $(SHLIB_EXPORTS:%.txt=%.list)
   ifneq (,$(exports_file))
     exported_symbols_list = -exported_symbols_list $(exports_file)
@@ -142,7 +142,7 @@ ifeq ($(PORTNAME), openbsd)
   ifdef soname
     LINK.shared		+= -Wl,-x,-soname,$(soname)
   endif
-  BUILD.exports		= ( echo '{ global:'; $(AWK) '/^[^\#]/ {printf "%s;\n",$$1}' $<; echo ' local: *; };' ) >$@
+  BUILD.exports		= ( echo '{ global:'; $(AWK) '/^[^\043]/ {printf "%s;\n",$$1}' $<; echo ' local: *; };' ) >$@
   exports_file		= $(SHLIB_EXPORTS:%.txt=%.list)
   ifneq (,$(exports_file))
     LINK.shared		+= -Wl,--version-script=$(exports_file)
@@ -158,7 +158,7 @@ ifeq ($(PORTNAME), freebsd)
   ifdef soname
     LINK.shared		+= -Wl,-x,-soname,$(soname)
   endif
-  BUILD.exports		= ( echo '{ global:'; $(AWK) '/^[^\#]/ {printf "%s;\n",$$1}' $<; echo ' local: *; };' ) >$@
+  BUILD.exports		= ( echo '{ global:'; $(AWK) '/^[^\043]/ {printf "%s;\n",$$1}' $<; echo ' local: *; };' ) >$@
   exports_file		= $(SHLIB_EXPORTS:%.txt=%.list)
   ifneq (,$(exports_file))
     LINK.shared		+= -Wl,--version-script=$(exports_file)
@@ -170,7 +170,7 @@ ifeq ($(PORTNAME), netbsd)
   ifdef soname
     LINK.shared		+= -Wl,-x,-soname,$(soname)
   endif
-  BUILD.exports		= ( echo '{ global:'; $(AWK) '/^[^\#]/ {printf "%s;\n",$$1}' $<; echo ' local: *; };' ) >$@
+  BUILD.exports		= ( echo '{ global:'; $(AWK) '/^[^\043]/ {printf "%s;\n",$$1}' $<; echo ' local: *; };' ) >$@
   exports_file		= $(SHLIB_EXPORTS:%.txt=%.list)
   ifneq (,$(exports_file))
     LINK.shared		+= -Wl,--version-script=$(exports_file)
@@ -215,7 +215,7 @@ ifeq ($(PORTNAME), linux)
   ifdef soname
     LINK.shared		+= -Wl,-soname,$(soname)
   endif
-  BUILD.exports		= ( echo '{ global:'; $(AWK) '/^[^\#]/ {printf "%s;\n",$$1}' $<; echo ' local: *; };' ) >$@
+  BUILD.exports		= ( echo '{ global:'; $(AWK) '/^[^\043]/ {printf "%s;\n",$$1}' $<; echo ' local: *; };' ) >$@
   exports_file		= $(SHLIB_EXPORTS:%.txt=%.list)
   ifneq (,$(exports_file))
     LINK.shared		+= -Wl,--version-script=$(exports_file)

src/backend/Makefile

@@ -95,14 +95,14 @@ SYMBOL_MAPPING_FLAGS =
 ifeq ($(PORTNAME), darwin)
 SYMBOL_MAP_FILE = hide_symbols.list
 $(SYMBOL_MAP_FILE): $(top_builddir)/src/interfaces/libpq/exports.txt
-	$(AWK) '/^[^\#]/ {printf "_%s\n",$$1}' $< | grep -v -E $(SAFELY_EXPORTED_SYMBOLS_PATTERN) >$@
+	$(AWK) '/^[^\043]/ {printf "_%s\n",$$1}' $< | grep -v -E $(SAFELY_EXPORTED_SYMBOLS_PATTERN) >$@
 SYMBOL_MAPPING_FLAGS = -unexported_symbols_list $(SYMBOL_MAP_FILE)
 endif
 
 ifeq ($(PORTNAME), linux)
 SYMBOL_MAP_FILE = postgres_symbols.map
 $(SYMBOL_MAP_FILE): $(top_builddir)/src/interfaces/libpq/exports.txt
-	( echo '{ global: *; '; echo ' local:'; $(AWK) '/^[^\#]/ {printf "%s;\n",$$1}' $< | grep -v -E $(SAFELY_EXPORTED_SYMBOLS_PATTERN); echo '};' ) >$@
+	( echo '{ global: *; '; echo ' local:'; $(AWK) '/^[^\043]/ {printf "%s;\n",$$1}' $< | grep -v -E $(SAFELY_EXPORTED_SYMBOLS_PATTERN); echo '};' ) >$@
 SYMBOL_MAPPING_FLAGS = -Wl,--version-script=$(SYMBOL_MAP_FILE)
 endif
 ifeq ($(enable_shared_postgres_backend),yes)