How to get the list of targets in a makefile

Lazy Set

VARIABLE = value

Normal setting of a variable, but any other variables mentioned with the value field are recursively expanded with their value at the point at which the variable is used, not the one it had when it was declared

Immediate Set

VARIABLE := value

Setting of a variable with simple expansion of the values inside - values within it are expanded at declaration time.

Lazy Set If Absent

VARIABLE ?= value

Setting of a variable only if it doesn't have a value. value is always evaluated when VARIABLE is accessed. It is equivalent to

ifeq ($(origin VARIABLE), undefined)
  VARIABLE = value
endif

See the documentation for more details.

Append

VARIABLE += value

Appending the supplied value to the existing value (or setting to that value if the variable didn't exist)

From the GNU Make documentation,

5.3.1 Choosing the Shell
------------------------

The program used as the shell is taken from the variable `SHELL'.  If
this variable is not set in your makefile, the program `/bin/sh' is
used as the shell.

So put SHELL := /bin/bash at the top of your makefile, and you should be good to go.

BTW: You can also do this for one target, at least for GNU Make. Each target can have its own variable assignments, like this:

all: a b

a:
    @echo "a is $$0"

b: SHELL:=/bin/bash   # HERE: this is setting the shell for b only
b:
    @echo "b is $$0"

That'll print:

a is /bin/sh
b is /bin/bash

See "Target-specific Variable Values" in the documentation for more details. That line can go anywhere in the Makefile, it doesn't have to be immediately before the target.