There may be an error in this? Not sure, but in my code, I'm getting an error. I removed @ from the beginning the shell code in Makefile so that I can see the output:

if test "xgi.o" != "x" ; then \
/usr/local/pike/8.0.610/include/pike/install_module module.so /usr/local/pike/8.0.610/lib/modules/___GI.so && \
fi; \
if test "x./module.pmod.in" != "x"; then \
/usr/local/pike/8.0.610/include/pike/install_module module.pmod /usr/local/pike/8.0.610/lib/modules/GI.pmod ;\
fi;
/bin/sh: -c: line 2: syntax error near unexpected token `fi'
/bin/sh: -c: line 2: `fi; \'
make: *** [Makefile:449: install] Error 1

The error is the && at the end of ___GI.so above, it should be replaced with ; (semicolon).

Although looking at PIke-8.0.610/src/modules/dynamic_module_makefile.in, I see this:

#
# install a standard module with optional c component in the system module path
#
install: $(MODULE_INSTALL)
        @if test "x$(OBJS)" != "x" ; then \
          $(TMP_BINDIR)/install_module module.so $(SYSTEM_MODULE_PATH)/$(MODDIR)$(MODULE_WRAPPER_PREFIX)$(MODNAME).so && \
          if [ -f $(MODNAME).pdb ]; then \
            cp $(MODNAME).pdb $(SYSTEM_MODULE_PATH)/$(MODDIR)$(MODULE_WRAPPER_PREFIX); \
          else :; fi; \
        fi; \
        if test "x$(MODULE_PMOD_IN)" != "x"; then \
          $(TMP_BINDIR)/install_module module.pmod $(SYSTEM_MODULE_PATH)/$(MODDIR)$(MODNAME).pmod ;\
        fi;

Which is different from my generated Makefile:

#
# install a standard module with optional c component in the system module path
#
install: $(MODULE_INSTALL)
        @if test "x$(OBJS)" != "x" ; then \
          $(TMP_BINDIR)/install_module module.so $(SYSTEM_MODULE_PATH)/$(MODDIR)$(MODULE_WRAPPER_PREFIX)$(MODNAME).so && \
        fi; \
        if test "x$(MODULE_PMOD_IN)" != "x"; then \
          $(TMP_BINDIR)/install_module module.pmod $(SYSTEM_MODULE_PATH)/$(MODDIR)$(MODNAME).pmod ;\
        fi;

So mine might be getting dynamic_module_makefile.in from somewhere else...

Hmm, so removed /usr/local/pike/8.0.610/include/pike/modules/dynamic_module_makefile, and did a reinstall (sudo make install) of pike from Pike-8.0.610, and the proper code (2 stanzas above) got output to the incorrect code (just above) in my file, which is causing problems doing pike -x module install.

So it looks like the part:

if [ -f $(MODNAME).pdb ]; then \
cp $(MODNAME).pdb $(SYSTEM_MODULE_PATH)/$(MODDIR)$(MODULE_WRAPPER_PREFIX); \

else :; fi; \

is being removed for some reason, which is causing a problem with && being improper syntax for the resulting shell code.

Weird...