depends: Defer to Python detected by autoconf

Since autoconf already detects the correct python binary path, we should
use that instead of going around it. Also has the benefit of working in
extremely restricted environments where /usr/bin/env might not be
available.

Author: dongcarl

src/Makefile.am

@@ -642,13 +642,13 @@ clean-local:
 check-symbols: $(bin_PROGRAMS)
 if GLIBC_BACK_COMPAT
 	@echo "Checking glibc back compat..."
-	$(AM_V_at) READELF=$(READELF) CPPFILT=$(CPPFILT) $(top_srcdir)/contrib/devtools/symbol-check.py < $(bin_PROGRAMS)
+	$(AM_V_at) READELF=$(READELF) CPPFILT=$(CPPFILT) $(PYTHON) $(top_srcdir)/contrib/devtools/symbol-check.py < $(bin_PROGRAMS)
 endif
 
 check-security: $(bin_PROGRAMS)
 if HARDEN
 	@echo "Checking binary security..."
-	$(AM_V_at) READELF=$(READELF) OBJDUMP=$(OBJDUMP) $(top_srcdir)/contrib/devtools/security-check.py < $(bin_PROGRAMS)
+	$(AM_V_at) READELF=$(READELF) OBJDUMP=$(OBJDUMP) $(PYTHON) $(top_srcdir)/contrib/devtools/security-check.py < $(bin_PROGRAMS)
 endif
 
 if ENABLE_BIP70