buildinfo: move from tests/server/ to src/, rename to curlinfo

Since a16485a42e, the test servers build with a different set of
options than the tool/lib - for example a different CURLDEBUG. To make
buildinfo better reflect the curl build, move it to src/ and build it
here using the local CURLDEBUG. Renamed to curlinfo to not get confused
with buildinfo.txt

I chose src/ and not lib/ because the file also uses tool-specific headers.

Assisted-by: Viktor Szakats
Closes #17187

src/Makefile.am

@@ -48,6 +48,9 @@ AM_CPPFLAGS = -I$(top_srcdir)/include        \
 
 bin_PROGRAMS = curl
 
+curlinfo_SOURCES = curlinfo.c
+noinst_PROGRAMS = curlinfo
+
 if USE_CPPFLAG_CURL_STATICLIB
 AM_CPPFLAGS += -DCURL_STATICLIB
 endif
@@ -60,7 +63,7 @@ endif
 
 AM_LDFLAGS =
 if USE_UNICODE
-AM_LDFLAGS += -municode
+UNICODEFLAG = -municode
 endif
 
 include Makefile.inc
@@ -90,7 +93,7 @@ curl_SOURCES += $(CURL_RCFILES)
 $(CURL_RCFILES): tool_version.h
 endif
 
-curl_LDFLAGS = $(AM_LDFLAGS) $(CURL_LDFLAGS_BIN)
+curl_LDFLAGS = $(AM_LDFLAGS) $(CURL_LDFLAGS_BIN) $(UNICODEFLAG)
 
 # This might hold -Werror
 CFLAGS += @CURL_CFLAG_EXTRAS@