Makefile.am: avoid double `bison` execution on parallel build
Before the change `make -j16` ran `bison` twice on the same input:
$ make -j16
...
make[1]: Entering directory '/build/source/Source'
bison -d -Wall -Werror --output=CParse/parser.c ./CParse/parser.y
gcc -g -O2 -Wall -W -I. -c -o mdfour.o mdfour.c
bison -d -Wall -Werror --output=CParse/parser.c ./CParse/parser.y
...
Note how two parallel `bison` calls both generate the same files. It works
most of the time, but is prone to generate unexpected output.
This happens because Makefile rules like:
a b: c; COMMAND
all: a b
will run COMMAND for each target (twice here: once for `a` and once for
`b`),
The fix uses GNU make's Grouped Targets to use single command to produce
multiple targets.
1 file changed
