Trac #15624: Support "make -jN"

This should be supported by the top-level `Makefile`:
{{{
$ make -j4
}}}

The branch on this ticket implements this for sub-`make`s. For uses of
`$MAKE` outside of `make` itself (like building the Sage documentation
or Sage library), the value of `-j` given to `make` cannot be determined
so this cannot work.

URL: http://trac.sagemath.org/15624
Reported by: jdemeyer
Ticket author(s): Jeroen Demeyer
Reviewer(s): Peter Bruin

Makefile

@@ -16,7 +16,7 @@ logs:
 	mkdir -p $@
 
 build: logs configure
-	cd build && \
+	+cd build && \
 	"../$(PIPE)" \
 		"env SAGE_PARALLEL_SPKG_BUILD='$(SAGE_PARALLEL_SPKG_BUILD)' ./install all 2>&1" \
 		"tee -a ../logs/install.log"

build/install

@@ -310,9 +310,10 @@ fi
 # Create $SAGE_ROOT/build/Makefile starting from build/deps
 ###############################################################################
 
-exec 3>Makefile
+# Trac #15624: use file descriptor 5 since make uses 3 and 4
+exec 5>Makefile
 
-cat >&3 <<EOF
+cat >&5 <<EOF
 #==============================================================================
 # This file has been automatically generated by
 #   $SAGE_ROOT/build/install
@@ -323,16 +324,16 @@ EOF
 
 # Use bash as shell for the Makefile (bash obviously exists, since
 # this build/install script runs under bash).
-echo >&3 "SHELL = `command -v bash`"
-echo >&3
+echo >&5 "SHELL = `command -v bash`"
+echo >&5
 
 # If the user (or the Makefile) has set SAGE_PARALLEL_SPKG_BUILD=no,
 # then turn off parallel building: disable just building multiple
 # packages at the same time.   Individual packages can still be built
 # in parallel by specifying '-j' in $MAKE.
 if [ "${SAGE_PARALLEL_SPKG_BUILD:-yes}" = no ]; then
-    echo ".NOTPARALLEL:" >&3
-    echo "" >&3
+    echo ".NOTPARALLEL:" >&5
+    echo "" >&5
 fi
 
 # Usage: newest_version $pkg
@@ -349,7 +350,7 @@ newest_version() {
     fi
 }
 
-cat >&3 <<EOF
+cat >&5 <<EOF
 # Standard packages
 ATLAS=`newest_version atlas`
 BOEHM_GC=`newest_version boehm_gc`
@@ -445,40 +446,40 @@ INST=`echo "$SAGE_SPKG_INST" | sed 's/ /\\\\ /g'`
 EOF
 
 # $(TOOLCHAIN) variable containing prerequisites for the build
-echo >&3 -n 'TOOLCHAIN ='
+echo >&5 -n 'TOOLCHAIN ='
 if [ "$SAGE_INSTALL_CCACHE" = yes ]; then
-    echo >&3 -n ' $(INST)/ccache'
+    echo >&5 -n ' $(INST)/ccache'
 fi
 if [ "$need_to_install_gcc" = yes ]; then
-    echo >&3 -n ' $(INST)/$(GCC)'
+    echo >&5 -n ' $(INST)/$(GCC)'
     # Use this option for the prereq configure script, such that it
     # will skip all compiler checks.
     export PREREQ_OPTIONS="--disable-compiler-checks $PREREQ_OPTIONS"
 fi
-echo >&3
+echo >&5
 
-echo >&3 'SCRIPT_SOURCES = \'
+echo >&5 'SCRIPT_SOURCES = \'
 for file in "$SAGE_SRC/bin/"*; do
-    echo >&3 "                 \$(SAGE_SRC)${file#$SAGE_SRC} \\"
+    echo >&5 "                 \$(SAGE_SRC)${file#$SAGE_SRC} \\"
 done
-echo >&3
-echo >&3 'SCRIPTS = \'
+echo >&5
+echo >&5 'SCRIPTS = \'
 for file in "$SAGE_SRC/bin/"*; do
-    echo >&3 "                 \$(SAGE_LOCAL)${file#$SAGE_SRC} \\"
+    echo >&5 "                 \$(SAGE_LOCAL)${file#$SAGE_SRC} \\"
 done
-echo >&3
-echo >&3 'EXTCODE_SOURCES = \'
+echo >&5
+echo >&5 'EXTCODE_SOURCES = \'
 for file in `find "$SAGE_SRC"/ext -type f`; do
-    echo >&3 "                  \$(SAGE_SRC)${file#$SAGE_SRC} \\"
+    echo >&5 "                  \$(SAGE_SRC)${file#$SAGE_SRC} \\"
 done
-echo >&3
-echo >&3 'EXTCODE = \'
+echo >&5
+echo >&5 'EXTCODE = \'
 for file in `find "$SAGE_SRC"/ext -type f`; do
-    echo >&3 "                  \$(SAGE_EXTCODE)${file#$SAGE_SRC/ext} \\"
+    echo >&5 "                  \$(SAGE_EXTCODE)${file#$SAGE_SRC/ext} \\"
 done
-echo >&3
+echo >&5
 
-cat >&3 <<EOF
+cat >&5 <<EOF
 # don't just use \`install\` since we don't want to change permissions
 \$(SAGE_LOCAL)/bin/%: \$(SAGE_SRC)/bin/%
 	cp \$< \$@
@@ -492,7 +493,7 @@ cat >&3 <<EOF
 EOF
 
 # Copy build/deps
-cat >&3 <<EOF
+cat >&5 <<EOF
 
 #==============================================================================
 # What follows now is a copy of
@@ -501,10 +502,10 @@ cat >&3 <<EOF
 
 EOF
 
-cat "$SAGE_ROOT/build/deps" >&3
+cat "$SAGE_ROOT/build/deps" >&5
 
 # Close the Makefile
-exec 3>&-
+exec 5>&-
 
 ###############################################################################
 # Skip the rest if nothing to do (i.e., to [re]build).